WASHINGTON — George Nader, a Lebanese-American businessman, has hovered on the fringes of international diplomacy for three decades. He was a back-channel negotiator with Syria during the Clinton administration, reinvented himself as an adviser to the de facto ruler of the United Arab Emirates, and last year was a frequent visitor to President Trump’s White House.
Mr. Nader is now a focus of the investigation by Robert S. Mueller III, the special counsel. In recent weeks, Mr. Mueller’s investigators have questioned Mr. Nader and have pressed witnesses for information about any possible attempts by the Emiratis to buy political influence by directing money to support Mr. Trump during the presidential campaign, according to people with knowledge of the discussions.
The investigators have also asked about Mr. Nader’s role in White House policymaking, those people said, suggesting that the special counsel investigation has broadened beyond Russian election meddling to include Emirati influence on the Trump administration. The focus on Mr. Nader could also prompt an examination of how money from multiple countries has flowed through and influenced Washington during the Trump era.
How much this line of inquiry is connected to Mr. Mueller’s original task of investigating contacts between Mr. Trump’s campaign and Russia is unclear. The examination of the U.A.E. comes amid a flurry of recent activity by Mr. Mueller.
Last month, investigators negotiated a plea agreement with Rick Gates, Mr. Trump’s deputy campaign manager, and indicted 13 Russians on charges related to a scheme to incite political discord in the United States before the 2016 election.
Mr. Broidy owns a private security company with hundreds of millions of dollars in contracts with the United Arab Emirates, and he extolled to Mr. Trump a paramilitary force that his company was developing for the country. He also lobbied the president to meet privately “in an informal setting” with the Emirates’ military commander and de facto ruler, Crown Prince Mohammed bin Zayed al-Nahyan; to back the U.A.E.’s hawkish policies in the region; and to fire Secretary of State Rex W. Tillerson.
A copy of Mr. Broidy’s memorandum about the meeting was provided to The New York Times by someone critical of the Emirati influence in Washington.
Mr. Trump has closely allied himself with the Emiratis, endorsing their strong support for the new heir to the throne in Saudi Arabia, as well as their confrontational approaches toward Iran and their neighbor Qatar. In the case of Qatar, which is the host to a major United States military base, Mr. Trump’s endorsement of an Emirati- and Saudi-led blockade against that country has put him openly at odds with his secretary of state — as well as with years of American policy.
Mr. Nader, 58, made frequent trips to the White House during the early months of the Trump administration, meeting with Stephen K. Bannon and Jared Kushner to discuss American policy toward the Persian Gulf states in advance of Mr. Trump’s trip to Saudi Arabia in May 2017, according to people familiar with the meetings. By some accounts, it was Mr. Bannon who pushed for him to gain access to White House policymakers. Others said Mr. Kushner backed him.
Reached by phone last month, Mr. Nader said he had dinner guests and would call back. He did not, and attempts to reach him over several weeks were unsuccessful. Mr. Nader’s lawyer did not respond to messages seeking comment.
The White House did not respond to requests for comment. In a statement, a spokesman for Mr. Broidy said his memorandum had been stolen through sophisticated hacking.
Yousef al-Otaiba, the Emirati ambassador to the United States, declined to comment. Axios first reported Mr. Mueller’s questioning of Mr. Nader.
Mr. Nader has long been a mysterious figure. In the 1990s, he presided over an unusual Washington magazine, Middle East Insight, which sometimes provided a platform for Arab, Israeli and Iranian officials to express their views to a Washington audience.
On the magazine’s 15th anniversary, in 1996, a West Virginia congressman praised Mr. Nader on the floor of the House, calling him a “recognized expert on the region” and pointing out that the magazine had been a showcase for prominent figures such as President Hosni Mubarak of Egypt, Prime Minister Yitzhak Rabin of Israel, and Yasir Arafat, the head of the Palestine Liberation Organization.
“He always struck me as a person who really thought he should be in the eye of the storm trying to make things happen,” said Frederic Hof, a former top American diplomat who knew Mr. Nader in the 1990s.
Late in that decade, Mr. Nader convinced the Clinton administration that he had valuable contacts in the Syrian government and took on a secretive role trying to broker a peace deal between Israel and Syria. Working with Ronald S. Lauder, the American cosmetics magnate and prominent donor to Jewish causes, Mr. Nader shuttled between Damascus and Jerusalem, using his contacts in both capitals to try to negotiate a truce.
“In the 1990s, George was a very effective under-the-radar operator in the peace process,” said Martin S. Indyk, a former American ambassador to Israel and a member of a team put together by President Bill Clinton to negotiate peace deals between Israel and its neighbors.
“Then, he disappeared.”
Indeed, a man with a once very public profile in Washington effectively vanished from the capital’s policy scene, and his magazine ceased publication in 2002.
During the middle part of the last decade, Mr. Nader appears to have spent most of his time in the Middle East, especially in Iraq after the 2003 invasion. He developed close ties to national security officials in the Bush White House.
Erik Prince, the founder of Blackwater USA, the private security company now known as Academi, at one point hired Mr. Nader to help the company generate business deals in Iraq. In a 2010 deposition that Mr. Prince gave as part of a lawsuit against the company, Mr. Prince described Mr. Nader as a “business development consultant that we retained in Iraq” because the company was looking for contracts with the Iraqi government.
Mr. Prince said that Mr. Nader was unsuccessful in getting contracts, and that senior Blackwater officials did not work directly with him.
“George pretty much worked on his own,” he said.
At the beginning of the Obama era, Mr. Nader tried to parlay his ties to the Syrian government into access to senior members of President Barack Obama’s foreign policy team, while also seeking to advance business deals with former advisers to President George W. Bush.
By the time of the 2016 election, he had become an adviser to Prince Mohammed of the U.A.E. According to people familiar with the relationship, it was around Mr. Trump’s inauguration that Mr. Nader first met Mr. Broidy, the Republican fund-raiser, who is a California-based investor with a strong interest in the Middle East.
Mr. Broidy’s security company, Circinus, provides services to both United States agencies and foreign governments. Run by former American military officers, Circinus promises on its website that it “can employ personnel worldwide to provide physical force protection to individuals, groups or facilities within austere, hostile environments,” as well as conducting “specialized operations, infrastructure protection and training.”
Mr. Broidy, 60, had once stumbled into legal trouble over payments to a political figure. In 2009, he agreed to plead guilty to a misdemeanor charge for providing $1 million in illegal gifts to New York State pension authorities, including trips, payouts and a secret investment in a film called “Chooch” that was produced by an official’s brother. In exchange for the gifts, the state pension fund invested $250 million with an Israeli-based investment management firm that Mr. Broidy had founded. He reimbursed the pension fund for $18 million in fees.
After the inauguration, Mr. Nader became friendly with Mr. Broidy and introduced him to Prince Mohammed. Circinus then signed contracts with the United Arab Emirates worth several hundred million dollars, according to people familiar with the arrangement.
By Oct. 6, Mr. Broidy had evidently become close enough to both the prince and Mr. Nader to send a detailed memorandum to an encrypted email address used by Mr. Nader recounting his advocacy on the U.A.E.’s behalf during the meeting with Mr. Trump in the Oval Office amid an afternoon of stops throughout the White House.
An ally of the White House involved in one of the initiatives discussed — a counterterrorism task force — said Mr. Broidy sent the memorandum because he had been asked by the crown prince to seek the president’s views on the idea. Mr. Broidy believed that the creation of the task force would aid American security, this person said.
According to the memo, Mr. Broidy repeatedly pressed Mr. Trump to meet privately with Prince Mohammed, preferably in an informal setting outside the White House.
“I offered that M.B.Z. is available to come to the U.S. very soon and preferred a quiet meeting in New York or New Jersey,” Mr. Broidy wrote to Mr. Nader, using the crown prince’s initials. “President Trump agreed that a meeting with M.B.Z. was a good idea.”
Mr. Broidy wrote that he had twice told Lt. Gen. H. R. McMaster, the national security adviser, that the crown prince “preferred an informal setting to meet one on one with President Trump.” But General McMaster resisted. “LTG McMaster smiled and replied that heads of state usually meet in the White House,” as “protocol dictates.”
In his memorandum, Mr. Broidy recounted that he had told Mr. Trump that he recently returned from meeting with the crown prince about Circinus work for the U.A.E. Mr. Broidy had explained “the exciting and transformational plan being constructed by M.B.Z. to develop a counterterrorism task force,” which Mr. Broidy told the president was “inspired” by his speech at a conference in Riyadh.
Mr. Broidy was harshly critical of the crown prince’s neighbor and nemesis, Qatar. The U.A.E. has accused Qatar, an American ally, of using its satellite network Al Jazeera to promote political Islam, among other allegations.
Mr. Trump also asked about Mr. Tillerson — who had publicly criticized the isolation of Qatar — and Mr. Broidy said that the secretary of state should be fired. “Rex was performing poorly,” Mr. Broidy said, according to the memorandum.
In between the discussions of diplomacy, business and statecraft, Mr. Broidy wrote, he and the president “spoke for several minutes about politics and the fund-raising efforts for the midterm elections as well as the state of affairs at the R.N.C.,” or the Republican National Committee.