WASHINGTON (AP) - Days before he was fired by Donald Trump, FBI Director James Comey requested more resources to pursue his investigation into Russia's election meddling and the possible involvement of Trump associates, U.S. officials say, fueling concerns that Trump was trying to undermine a probe that could threaten his presidency.
It was unclear whether word of the Comey request, put to Deputy Attorney General Rod Rosenstein, ever made its way to Trump. But the revelation intensified the pressure on the White House from both political parties to explain the motives behind Comey's stunning ouster.
Trump is the first president since Richard Nixon to fire a law enforcement official overseeing an investigation with ties to the White House. Democrats quickly accused Trump of using Comey's handling of the Hillary Clinton email investigation as a pretext and called for a special prosecutor into the Russia probe. Republican leaders brushed off the idea as unnecessary.
Defending the firing, White House officials said Trump's confidence in Comey had been eroding for months. They suggested Trump was persuaded to take the step by Justice Department officials and a scathing memo, written by Rosenstein, criticizing the director's role in the Clinton investigation.
"Frankly, he'd been considering letting Director Comey go since the day he was elected," White House spokeswoman Sarah Huckabee Sanders said, a sharply different explanation from the day before, when officials put the emphasis on new Justice complaints about Comey.
Trump's action left the fate of the Russia probe deeply uncertain. The investigation has shadowed Trump from the outset of his presidency, though he's denied any ties to Russia or knowledge of campaign coordination with Moscow.
Trump, in a letter to Comey dated Tuesday, contended that the director had told him "three times" that he was not personally under investigation. The White House refused Wednesday to provide any evidence or greater detail. Former FBI agents said such a statement by the director would be all but unthinkable.
Sanders, speaking Thursday on ABC's "Good Morning America," said, "I have heard that directly from him (Trump), that that information was relayed directly to him from Director Comey." On NBC's "Today," Sanders said she would defer to the president himself for any additional details.
Outraged Democrats called for an independent investigation into the Trump campaign's possible ties to Russia's election interference, and a handful of prominent Republican senators left open that possibility. But Senate Majority Leader Mitch McConnell, with the support of the White House, brushed aside those calls, saying a new investigation would only "impede the current work being done."
The Senate intelligence committee on Wednesday subpoenaed former Trump national security adviser Michael Flynn for documents related to its investigation into Russia's election meddling. Flynn's Russia ties are also being scrutinized by the FBI.
Acting FBI Director Andrew McCabe was scheduled to testify Thursday before the Senate Intelligence Committee at an annual hearing on worldwide threats.
The White House appeared caught off guard by the intense response to Comey's firing, given that the FBI director had become a pariah among Democrats for his role in the Clinton investigation. In defending the decision, officials leaned heavily on a memo from Rosenstein, the deputy attorney general, criticizing Comey's handling of the Clinton investigation.
But Rosenstein's own role in Comey's firing became increasingly murky Wednesday.
Three U.S. officials said Comey recently asked Rosenstein for more manpower to help with the Russia investigation. Sen. Dick Durbin, D-Ill., said that while he couldn't be certain the request triggered Comey's dismissal, he said he believed the FBI "was breathing down the neck of the Trump campaign and their operatives and this was an effort to slow down the investigation."
Justice Department spokeswoman Sarah Isgur Flores denied that Comey had asked Rosenstein for more resources for the Russia investigation.
Trump advisers said the president met with Rosenstein, as well as Attorney General Jeff Sessions, on Monday after learning that they were at the White House for other meetings. One official said Trump asked Rosenstein and Sessions for their views on Comey, then asked the deputy attorney general to synthesize his thoughts in a memo.
The president fired Comey the following day. The White House informed Comey by sending him an email with several documents, including Rosenstein's memo.
It's unclear whether Rosenstein was aware his report would be used to justify the director's ouster.
White House and other U.S. officials insisted on anonymity to disclose private conversations.
A farewell letter from Comey that circulated among friends and colleagues said he does not plan to dwell on the decision to fire him or on "the way it was executed."
Trump is only the second president to fire an FBI director, underscoring the highly unusual nature of his decision. President Bill Clinton dismissed William Sessions amid allegations of ethical lapses in 1993.
The White House said the Justice Department was interviewing candidates to serve as interim FBI director while Trump weighs a permanent replacement. Sanders said the White House would "encourage" the next FBI chief to complete the Russia investigation.
"Nobody wants this to be finished and completed more than us," she said.
AP writers Darlene Superville, Ken Thomas, Vivian Salama, Catherine Lucey and Eric Tucker in Washington contributed to this report.