Richard Burr, R-North Carolina, and Mark Warner, D-Virginia, said it requested documents that members believe to be relevant to its investigation into alleged Russian meddling in the 2016 presidential election. Concerns have also been raised about undisclosed payments Flynn received from the Russia-backed TV network RT, and his unregistered lobbying that may have benefited Turkey, which took place when he was advising the Trump campaign.
Some of Mr Trump's fellow Republicans, including Mr Burr, also expressed strong doubts about the timing of the president's action.
The assessment comes amid a mushrooming crisis for the Trump team as questions swirl over why the president fired his FBI director, who was overseeing an investigation into Russian election meddling and possible connections between Trump campaign associates and Russia past year.
Former National Security Adviser Michael Flynn may not be able to dodge the senate Intelligence Committee much longer.
Michael Flynn was subpoenaed by the Senate Intelligence Committee as part of its investigation into links between Russian Federation and Mr Trump's campaign team.
President Donald Trump said one of the reasons why his administration kept national security adviser Michael Flynn on for 18 days after being briefed on his questionable conduct with Russian operatives, Trump said it was because the reports "did not sound like an emergency".
Princess Charlotte's Second Birthday Marked With New Royal Photo
The princess' hair is longer than when we last saw her at Christmas, and she's got a dark-blue clip keeping it tidy to the side. For Princess Charlotte's first birthday past year , Kensington Palace released four pictures of the little girl.
But senior Democrats said he had recently asked the Justice Department for more resources for his Trump-Russia investigation.
Russian Federation and the Trump administration deny any part in colluding on the USA election.
"No reasonable person, who has the benefit of advice from counsel, would submit to questioning in such a highly politicized, witch-hunt environment without assurances against unfair prosecution", he said.
He also said he called on Comey to ask for an update on a possible criminal investigation into his ties with Russian Federation.
Among the payments they cited were more than $33,000 from RT, a Russian state-sponsored television network that US intelligence officials have branded as a propaganda front for Russia's government. The disagreement points to inconsistencies in Flynn's accounts to the US government about his work for foreign interests. The difference matters because Flynn's foreign business relationships and the veracity of his disclosures are under scrutiny by congressional, military and intelligence inquiries.