After the meeting, the two presidents held a common press conference in which Donald Trump praised Klaus Iohannis for leading the fight against corruption in Romania and for the country's efforts to increase its defense spending.
As he did in a message on Twitter Friday morning, Trump called Comey a "leaker".
"Absolutely, I'd be committed to Article 5", Trump said responding to a question on North Atlantic Treaty Organisation.
The Times issued a statement late Thursday evening saying the publication would review any information that might disprove the original story but noting that "neither the Federal Bureau of Investigation, nor Mr. Comey would comment or elaborate on what Mr. Comey believes to be incorrect".
During nearly three hours of statements Thursday before the Senate Intelligence Committee, Comey described himself as "stunned" by Trump's "very disturbing" and "very concerning" behavior towards him.
He has already hosted British Prime Minister Theresa May, whose party lost seats, at the White House earlier this year. For the first time since taking office in January, Trump said he would honor the U.S.' commitment to NATO Article 5.
President Trump on Friday accused former FBI director James B. Comey of lying under oath to Congress in the Russian Federation investigation and called him a "leaker", before suggesting he would be willing to give his side of the story to special counsel Robert Mueller.More news: United Kingdom election upset leaves prime minister's Brexit strategy in disarray
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"I found him to be credible, candid and thorough", Collins said of Comey on MSNBC's "Morning Joe".
Friday, Trump said some of Comey's remarks were true and some weren't.
"You're going to be very disappointed when you hear the answer, don't worry", Trump said. "But yes, absolutely, I'd be committed to Article 5".
"It was clear that the president asked Mr. Comey to do an inappropriate action, and that was to drop the investigation of General Michael Flynn", Senator Susan Collins told CNN. It was a stunning accusation, suggesting that the former Federal Bureau of Investigation director had lied to Congress, while under oath. I hardly know the man. "No I didn't say that".
In his first congressional appearance since being abruptly fired by Trump last month, Comey detailed months of distrust of the president and bluntly asserted that Trump had fired him to interfere with the probe of Russia's ties to the Trump campaign.
Harvard Law School professor Mark Tushnet said onlookers should keep in mind that Comey knows much more than he can say, calling his testimony a "big deal". Rather, Kasowitz said, Trump felt vindicated that Comey told him on several occasions that the president was not personally a focus of the investigation, an assertion Comey appeared to back up in his testimony Thursday to the Senate Intelligence Committee.
United States lawmakers will get another chance to hear from a top administration official, Attorney General Jeff Sessions, when he testifies Tuesday before the Senate Appropriations Committee.