James Comey led the United States Federal Bureau of Investigation (FBI) from September 2013 until May of 2017. Then, U.S. President Donald Trump ordered Comey's dismissal as FBI Director.

The war of words between Trump and Comey has heated up with the publication of Comey's new book. It is called A Higher Loyalty: Truth, Lies and Leadership.

Comey's ouster led the Justice Department to appoint former FBI Director Robert Mueller as special counsel. Mueller's team is investigating Russian involvement in the 2016 U.S. presidential election.

Comey spoke with ABC News about his new book. In a television program broadcast on Sunday night, Comey called Trump "morally unfit to be president." He also said that "it's possible" the Russians have something on Trump. And he added there is, in his words, "some evidence of obstruction of justice."

Even before the broadcast, Trump attacked Comey on Twitter. Trump called him "the WORST FBI Director in history" and a "slimeball." He wrote that Comey's writings "are self serving and FAKE!"

On Monday, the president accused Comey and former FBI deputy director Andrew McCabe of having "committed many crimes." McCabe was recently dismissed from the Trump administration.

‘A Higher Loyalty"

Comey's book tells about the FBI investigation of Russian interference in the 2016 elections. It offers Comey's version of the investigation on Hillary Clinton's use of a private email server while she was Secretary of State. The book also offers Comey's version of a private discussion with Trump about former White House national security adviser Michael Flynn.

Comey told Congress earlier that he and the president spoke about Flynn in private. Comey remembered Trump saying, "I hope you can see your way clear to letting this go." He also said that Trump told him during a private White House dinner in January 2017, "I need loyalty. I expect loyalty."

On Sunday, Trump rejected Comey's claim that he had sought Comey's loyalty. Trump wrote on Twitter, "I hardly even knew this guy. Just another of his many lies." He also suggested Comey should be imprisoned, tweeting, "how come he gave up Classified Information (jail), why did he lie to Congress (jail)."

Obstruction of justice

During the hour-long ABC News broadcast, Comey was asked if Trump was attempting to obstruct justice when he told other officials to leave the room before the meeting about Flynn. Comey answered, "it's possible."

At that time, Flynn was suspected of lying about his Russian contacts. The former national security adviser admitted guilt in court last December. He is now cooperating with the Mueller investigation.

During the broadcast, ABC reporter George Stephanopoulos asked, "Do you think the Russians have something on Donald Trump?" Comey said, "I think it's possible. I don't know." He did not offer any proof that Russia has anything on Trump.

Clinton email investigation

Comey also discussed the Clinton email investigation during the broadcast. He said his belief that Clinton would win the 2016 election was probably a factor in his decision to talk about the investigation.

He added, "I was operating in a world where Hillary Clinton was going to beat Donald Trump, and so I'm sure that it was a factor."

The admission led to strong criticism from Trump. He tweeted that Comey "was making decisions based on the fact that he thought she was going to win, and he wanted a job. Slimeball!"

Many Democratic Party activists blamed Comey for Clinton's loss. And Clinton herself has said his actions hurt her candidacy.

Stephanopoulos also asked Comey whether Congress should take legal action against Trump.

Comey answered, "I hope not because I think impeaching and removing Donald Trump from office would let the American people off the hook and have something happen indirectly that I believe they're duty-bound to do directly. People in this country need to stand up and go to the voting booth and vote their values."

Hai Do wrote this report for VOA Learning English. His report was based on stories from the Associated Press and transcript from ABC News. George Grow was the editor.