"By grandstanding and politicising the investigation into Russia's actions, James Comey created unnecessary pressure on our ability to engage and negotiate with Russia", Spicer said.
Journalists have since revealed several instances of undisclosed meetings between Trump's associates and Russians, or contacts that the White House initially mischaracterized.
The revelation undercuts President Donald Trump's insistence that his campaign had nothing to do with the Kremlin.
"The investigation would have always continued, and obviously, the termination of Comey would not have ended it", Spicer said, adding that the real story was the leaks of "private and highly classified conversations".
At first, the administration said Trump fired Comey based on the recommendation of the Justice Department, and because of Comey's handling of the FBI investigation into Hillary Clinton a year ago.
According to anonymous sources close to the White House, the administration has begun reviewing an obscure ethics rule in the Code of Federal Regulations, which could prevent Robert Mueller, the newly appointed special counsel, from investigating anyone who was a client of his law firm - which includes President Trump's son-in-law Jared Kushner and former campaign manager Paul Manafort. It is the first indication that the investigation is looking at a current senior White House adviser. It says the president then told Russia's foreign minister and ambassador that he "faced great pressure because of Russian Federation".
Former FBI Director James Comey has agreed to testify before an open meeting of the Senate Intelligence Committee, CNBC reports.
House of Representatives Minority Leader Nancy Pelosi said in response to the reports "every day the president gives us more reason to believe that he does not respect the office that he holds". "I also expect that Director Comey will be able to shed light on issues critical to this Committee's investigation of Russian interference in the 2016 election", said Vice Chairman Mark Warner, D-Va.
Trump's decision to fire Comey two weeks ago has fed into a maelstrom for his presidency. The date of the hearing has not yet been set.
Burr says the committee wants to hear from Comey on his role in the development of the USA intelligence agencies' assessment that Russian Federation interfered in last year's election.
President Trump fired Comey last week, setting off a political firestorm that included allegations that he is trying to influence the federal investigation into alleged collusion between his campaign and Russian Federation during the 2016 election. This week, Trump called the investigations a "witch hunt", in addition to releasing an official statement saying he looks forward to the "matter concluding quickly".
Comey is known to produce memos documenting especially sensitive or unsettling encounters, such as after the February meeting.
James Comey will come speak in a public sessions before the Senate Intelligence Committee sometime after Memorial Day, the committee announced Friday evening.