President Donald Trump invoked Pearl Harbor during a tense meeting with Japanese Prime Minister Shinzo Abe earlier this summer at the White House, is reporting.

"I remember Pearl Harbor," Trump told Abe in June, the prelude to a rant about the United States' trade deficit with Japan and his urging of Abe to redo the two countries' trade deal, the Post reports.

The comment caught Abe off-guard, given that he ostensibly has the best relationship with Trump of any foreign leader and Trump calls the prime minister his "good friend," the Post reports.

"I’ve never heard him [trash]-talk Abe. And you can’t say that about a lot of the world leaders," a U.S. official told the Post.

But it underscores the tension that exists even with Abe, whom Trump mostly ignored ahead of his denuclearization summit with North Korean leader Kim Jong Un earlier this year.

Regardless, U.S. officials who attended the meeting were at a loss to explain the Pearl Harbor comment.

"Although disturbing, this rhetoric hardly veers from Trump’s comments against Japan on the campaign trail," Shihoko Goto, a Japan expert at a Washington think tank, told the Post.

"His views of the Japanese economy then were based on the perceptions of the 1980s and ’90s, rather than the realities of today. So it may not be a surprise if his worldview, especially of Asia, is derived back from World War II, rather than today," Goto told the Post.