Comey testified that Trump previously told Comey he "hoped" the former FBI director would drop his Flynn investigation during an impromptu private meeting the two had in the Oval Office, a claim Trump Jr. argued isn't the same as a direct order from his dad.
Senator Collins, who is also a member of the Senate Intelligence Committee investigating Mr Trump's links to Russian Federation, described Mr Comey's testimony as "candid" and "thorough" and said she would support a subpoena if needed.
Trump was appearing in a Rose Garden press conference along with Romanian President Klaus Iohannis.
Mr Comey also has said Mr Sessions did not respond when he complained he did not "want to get time alone with the President again". "I'll tell you about it over a very short period of time", he said. That was an excuse by the Democrats, who lost an election they shouldn't have lost.
"I hardly know [Comey]. Who would ask a man to pledge allegiance under oath?" he said.
"Today we reaffirm and celebrate our strategic partnership that began more than 20 years ago", Trump said.
Comey's one-on-one discussions with Trump were the focal point of his testimony Thursday before the U.S. Senate Intelligence Committee. I mean, think of it.
Comey would not say whether he thought the president sought to obstruct justice, but added it would be up to special counsel Robert Mueller, who is now investigating the Russian Federation allegations, "to sort that out".
While he spoke, many on Twitter expressed their incredulity over Trump's Comey claims.
"Well, I'll tell you about that - maybe sometime in the very near future", Mr Trump said. "There were things Comey said in his testimony that were not true".
The president also denied having asked for a pledge of loyalty, as Comey asserted during Thursday's much-anticipated testimony.
"You are going to be very disappointed when you hear the answer", he said a bit cryptically.
During Comey's appearance before the intelligence committee, he stated he had written memos following meetings with Trump-something the former bureau chief said he had not done with previous presidents.
The White House later declined to provide a timeline for when such an announcement might be made.
"Lordy, I hope there are tapes", James Comey said when asked if the president suggested he may have recorded their phone conversations. "I'm not hinting anything".
He also said Trump asked him to drop the investigation into Flynn but steered clear of accusing the president of obstruction of justice.