Former national security adviser Michael Flynn's move to cooperate with the Federal Bureau of Investigation (FBI) has put the Donald Trump administration in a vulnerable position, say analysts.
Flynn had pleaded guilty last Friday to lying to the FBI about his contacts with Russia and agreed to cooperate with the FBI probe into possible collusion with Russia by the Trump campaign.
Special counsel Robert Mueller, who is heading the probe, now has "an ally who understands that he will only get a benefit if he 'cooperates' with the investigation, and that the meaning of 'cooperation' is entirely within the control of the prosecutors," Mr Jack Sharman told The Washington Post. He was a special counsel during investigations into president Bill Clinton in the 1990s.
Mr Joel B. Pollak, a senior editor at the conservative Breitbart News, wrote: "The information he (Flynn) provides will help Mueller hound anyone and everyone in the Trump orbit, in pursuit of the swamp's political revenge. And this is only the beginning." The "swamp" refers to Washington's bureaucracy and political elite.
"There's been absolutely no collusion," Mr Trump told reporters yesterday morning.
Those who could be vulnerable to the FBI's expanding investigation include Mr Trump's son-in-law Jared Kushner. Reports citing sources say Mr Kushner instructed Flynn to contact foreign ministers and ambassadors of countries on the United Nations Security Council - including the Russian ambassador - ahead of a vote condemning Israeli settlements, to oppose the resolution or delay the vote until Mr Obama had left office.
Ms K.T. McFarland, who was Flynn's deputy, is also said to be on the FBI's radar. She is the ambassador-designate to Singapore, but her appointment has not yet been confirmed.
"No skilled prosecutor makes an arrangement with a person who has as much legal liability as Michael Flynn unless he has excellent reasons to suspect Flynn has damaging information about people higher up," Professor Glenn Altschuler, who specialises in American Studies at Cornell University, told The Sunday Times.
Since last Friday, the White House has tried to distance itself from Flynn, with Mr Trump's lawyer calling him a Barack Obama-era official. But Flynn was actually fired from a post during the Obama administration.
Flynn was a key member of Mr Trump's campaign - and the President has repeatedly defended him.
Former FBI chief James Comey testified that Mr Trump had asked him to go easy on investigating Flynn. Soon after, the President fired Mr Comey.
The Trump administration could attack Mr Mueller.
Some of the President's more hawkish supporters - like his former strategist Steve Bannon - have advised firing him. But analysts warned that this risks igniting a political firestorm.
"I'm sure the White House is walking on eggshells right now," Mr Evan Siegfried, a Republican strategist, told The Sunday Times. "Based upon media reports, certainly Jared Kushner is in the cross hairs, and potentially even the President himself."
He added: "There is always a weak link for people and Flynn appears to be that for Trump."