Trump also complained about President Barack Obama's Nobel Peace Prize and doubted he would be similarly honored.
Prime Minister Shinzo Abe "gave me the most beautiful copy of a letter that he sent to the people who give out a thing called the Nobel Prize," Trump said at a White House news conference when asked about his late February summit in Vietnam with North Korean leader Kim Jong Un. "He said, 'I have nominated you, respectfully, on behalf of Japan. I am asking them to give you the Nobel Peace Prize.'"
The Associated Press could not immediately confirm Trump's claim.
Japan's Foreign Ministry said Saturday that it was aware of Trump's remark but cannot comment on details of the exchanges between Trump and Abe.
South Korean President Moon Jae-in, who also has credited Trump with starting negotiations with the reclusive North, has endorsed the U.S. leader for the Nobel Peace Prize as well.
Trump said early exchanges with Kim were filled with "fire and fury," but that the two have established a good relationship since their first meeting last year in Singapore. He said claimed Abe nominated him because he was worried about North Korea conducting missile tests over Japan.
Obama was awarded the Nobel Peace Prize in 2009, his first year in office, for laying out the U.S. commitment to "seek the peace and security of a world without nuclear weapons."
Trump complained Friday that Obama was there "for about 15 seconds" before he was awarded the prize.
"I'll probably never get it, but that's OK," Trump said. "They gave it to Obama. He didn't even know what he got it for."