WASHINGTON (NYTIMES) - President Donald Trump's lawyers and aides are scouring the professional and political backgrounds of investigators hired by the special counsel Robert Mueller, looking for conflicts of interest they could use to discredit the investigation - or even build a case to fire Mueller or get some members of his team recused, according to three people with knowledge of the research effort.

The search for potential conflicts is wide-ranging. It includes scrutinising donations to Democratic candidates, investigators' past clients and Mueller's relationship with James Comey, whose firing as FBI director is part of the special counsel's investigation.

The effort to investigate the investigators is another sign of a looming showdown between Trump and Mueller, who has assembled a team of high-powered prosecutors and agents to examine whether any of Trump's advisers aided Russia's campaign to disrupt last year's presidential election.

Some of the investigators have vast experience prosecuting financial malfeasance, and the prospect that Mueller's inquiry could evolve into an expansive examination of Trump's financial history has stoked fears among the president's aides. Both Trump and his aides have said publicly they are watching closely to ensure Mueller's investigation remains narrowly focused on last year's election.

During an interview with The New York Times on Wednesday (July 19), Trump said he was aware that members of Mueller's team had potential conflicts of interest and would make the information available "at some point".

Trump also said Mueller would be going outside his mandate if he begins investigating matters unrelated to Russia, like the president's personal finances. Trump repeatedly declined to say what he might do if Mueller appeared to exceed that mandate. But his comments to The Times represented a clear message to Mueller.

"The president's making clear that the special counsel should not move outside the scope of the investigation," Sarah Huckabee Sanders, a White House spokeswoman, said during a news briefing on Thursday.

Joshua Stueve, a spokesman for the special counsel, declined to comment.

For weeks, Republicans have publicly identified what they see as potential conflicts among Mueller's team of more than a dozen investigators. In particular, they have cited thousands of dollars of political donations to Democrats, including former President Barack Obama, made by Andrew Weissmann, a former senior Justice Department official who has expertise in fraud and other financial crimes. News reports have revealed similar donations by other members of Mueller's team, which Trump's allies have cited as evidence of political bias. Another lawyer Mueller has hired, Jeannie Rhee, represented the Clinton Foundation.

To seek a recusal, Trump's lawyers can argue their case to Mueller or his boss, Deputy Attorney General Rod Rosenstein. The Justice Department has explicit rules about what constitutes a conflict of interest. Prosecutors may not participate in investigations if they have "a personal or political relationship" with the subject of the case. Making campaign donations is not included on the list of things that would create a "political relationship".

The examination of Mueller's investigators reflects deep concerns among the president's aides that Mueller will mount a wide-ranging investigation in the mold of the inquiry conducted by the independent counsel Kenneth Starr during the 1990s. Starr's investigation into President Bill Clinton began by reviewing an Arkansas land deal and concluded several years later with the president's impeachment over a lie about a sexual affair.

By building files on Mueller's team, the Trump administration is following in the footsteps of the Clinton White House, which openly challenged Starr and criticised what Clinton's aides saw as a political witch hunt.

Trump's advisers are split on how far to go in challenging the independence of Mueller, a retired FBI director and one of the most respected figures in law enforcement. Some advisers have warned that dismissing Mueller would create a legal and political mess.

Nevertheless, Trump has kept up the attacks on him. In his interview with The Times, which caught members of his legal team by surprise, he focused on the fact that Mueller had interviewed to replace Comey as the FBI director just a day before Mueller was appointed special prosecutor, saying that the interview could create a conflict.

"He was sitting in that chair," Trump said during the Oval Office interview. "He was up here, and he wanted the job." Trump did not explain how the interview created a conflict of interest.

In addition to investigating possible collusion between Russia and Trump's advisers, the special counsel is examining whether the president obstructed justice by firing Comey. Some of Trump's supporters have portrayed Mueller and Comey as close friends. While they worked closely together in the Justice Department under President George W Bush and are known to respect each other, associates of both men say the two are not particularly close.

Mueller's team has begun examining financial records, and has requested documents from the IRS related to Trump's former campaign chairman, Paul Manafort, according to a senior US official. The records are from a criminal tax investigation that had been opened long before Trump's campaign began. Manafort was never charged in that case.

Federal investigators have also contacted Deutsche Bank about Trump's accounts, and the bank is expecting to provide information to Mueller.

A lawyer for Trump, Jay Sekulow, declined to address the potential conflicts he and the other lawyers for Trump have uncovered about Mueller's team. He said, however, that "any good lawyer would raise, at the appropriate time and in the appropriate venue, conflict-of-interest issues".

Sekulow is one part of a legal team in the midst of being reorganised, according to three people with knowledge of the matter. The role of Marc Kasowitz, the president's longtime New York lawyer, will be significantly reduced. Trump liked Kasowitz's blunt, aggressive style, but he was not a natural fit in the delicate, politically charged criminal investigation. The veteran Washington defence lawyer John Dowd will take the lead in representing Trump for the Russia inquiry.

Sekulow, a firebrand lawyer with deep conservative credentials, will serve as Dowd's deputy. Two people briefed on the new structure said it was created because the investigation is much more focused in Washington, where Dowd has a long history of dealing with the Justice Department.

Mark Corallo is no longer working as a spokesman for the legal team. A former Justice Department spokesman, Corallo was one of several people cautioning against publicly criticising Mueller.

The shake-up comes weeks after Dowd and Kasowitz had a face-to-face meeting with Mueller. The lawyers said they hoped Mueller would conduct a thorough investigation but asked that he wrap it up in a timely manner because of the cloud it had cast over the presidency, according to a senior US official and two others briefed on details of the meeting. Dowd said Trump would fully cooperate with Mueller, one of the people said.

It is not unusual for lawyers to meet with prosecutors to establish a line of communication, or to encourage them to move quickly. Trump's situation is unique, though, because of his team's public threats that they could fire Mueller at any time.