Donald Trump. Win McNamee/Getty Images

President Donald Trump asked the director of national intelligence and the director of the National Security Agency to push back against the FBI's Russia probe by publicly denying any collusion between the Trump campaign and Russian officials during the 2016 election, The Washington Post reported on Monday.

According to two current and former intelligence officials, Trump asked DNI Dan Coats and NSA director Adm. Michael Rogers separately to publicly deny collusion after former FBI director James Comey revealed the existence of the FBI's Russia inquiry during a March 20 testimony before the House Intelligence Committee. Both Coats and Rogers denied the request, because they believed it was inappropriate, the officials said.

Senior White House staff also spoke to top intelligence officials about the possibility of the White House directly intervening in the FBI's investigation, officials told the Post.

"Can we ask him to shut down the investigation? Are you able to assist in this matter?" a White House staffer asked, according to one intelligence official.

The Trump administration has been engulfed in controversy over the last two weeks, after he made the decision to fire Comey. Since then, it emerged that Trump had fired Comey because of "the Russia thing," as Trump put it, and that he had revealed highly-classified intelligence to Russian diplomats during an Oval Office meeting.

It was also reported that Trump asked Comey to drop the FBI's investigation into former national security adviser Michael Flynn during a February meeting, according to a memo that Comey wrote shortly after the meeting. The meeting, according to Comey's memo, took place one day after Flynn was forced to resign.

Last Wednesday, deputy attorney general Rod Rosenstein appointed former FBI director Robert Mueller to oversee the FBI's Trump-Russia investigation.

On Friday, The Washington Post reported that the FBI's probe reaches a senior White House adviser who is close to the president, according to people familiar with the matter.

Michael Flynn. AP Photo/Carolyn Kaster

Last week, The New York Times reported that the Trump transition team was aware that Flynn was under investigation before Trump took office. Flynn didn't resign until over a month later, and 18 days after former acting attorney general Sally Yates warned the White House that Flynn could be vulnerable to Russian blackmail.

On Monday, the Associated Press reported that Flynn will invoke his Fifth Amendment rights and decline a subpoena issued by the Senate Intelligence Committee for documents related to his interactions with Russian officials from June 2015 to January 2017.

The explosive reports that have emerged over the last few weeks have forced legal analysts and lawmakers to consider the possibility of presidential impeachment on obstruction of justice charges.

The "entire landscape of Trump's behavior" is what would prompt an obstruction of justice charge, said Jens David Ohlin, an associate dean at Cornell Law School and an expert on criminal law. That includes "telling Comey to back off on the Flynn investigation, firing him when he wouldn’t, and then admitting on national television that he dismissed Comey because of the Russia investigation."

If Trump knew for a fact that he was asking Coats and Rogers to make false statements, "then there's a very strong argument that he was trying to use them as an instrument to obstruct an on-going investigation," Ohlin said.

"That would be criminal, and a major data point for the ongoing FBI and congressional investigations," he added.

An obstruction of justice charge, however, also requires proof of corrupt intent, which is hard to pin down, according to Robert Deitz, a former top lawyer for the NSA and CIA. Rather, Deitz added, the question any lawyer would ask themselves would be whether they have enough evidence to persuade a jury.

"This latest story is yet one more piece of evidence that may cumulatively persuade," he said.

Trump's request to Coats and Rogers, senior intelligence officials said, threatened the independence of US spy agencies and could be seen as an attempt to question the FBI's credibility.

"The problem wasn’t so much asking them to issue statements, it was asking them to issue false statements about an ongoing investigation," an intelligence official told the Post.

"Things keep getting worse for the White House, though one bright spot for them is that reports indicate that Trump is close to selecting a personal attorney," Ohlin said. "Getting an attorney is a smart move."