Japan and North Korea held a “secret” meeting in Vietnam in July without informing the United States, the Washington Post reported Tuesday.

Shigeru Kitamura, head of Japan’s Cabinet Intelligence and Research Office, and a senior North Korean official in charge of reunification, Kim Song Hye, attended the talks, the newspaper said.

Senior U.S. officials expressed irritation that Japan was not forthright about the meeting despite Washington’s near-constant updates to Tokyo on its dealings with North Korea, it said.

Officials in Tokyo have acknowledged that to negotiate the return of Japanese abductees in North Korea, they cannot rely solely on the United States to lobby on Japan’s behalf, according to the paper.

U.S. President Donald Trump said after a historic summit with North Korean leader Kim Jong Un in June that he had raised the issue of North Korea’s abductions of Japanese nationals. But the joint statement issued by the leaders did not touch on human rights in North Korea, including the matter of abductions.

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Tokyo had asked Trump to take up with Kim the issue of Japanese citizens abducted by North Korea in the 1970s and 1980s. Pyongyang claims the matter has been settled.

The decades-old issue remains a stumbling block for Japan and North Korea to normalize diplomatic ties.

The Post report also detailed behind-the-scenes interactions said to have taken place between Trump and Abe — including a pointed remark about the U.S. entry into World War II that caught Abe off guard, it said.

During a tense meeting at the White House in June, Trump prefaced a blistering critique of Japan’s economic policies with the remark.

“I remember Pearl Harbor,” the Post quoted the president as saying, citing people familiar with the conversation, referring to the surprise attack on Dec. 7, 1941, that propelled the United States into World War II. Earlier reports by the Post state that Trump was born on June 14, 1946.

After making the comment, Trump then launched into his attack, according to the report, railing against the U.S. trade deficit with Japan and urging Abe to negotiate a bilateral trade deal that is more favorable to U.S. exporters of beef and automobiles.

The meeting, which was said to have left Abe exasperated, captured the paradoxical nature of what many say is Trump’s closest relationship with a foreign leader.

But in Tokyo, Chief Cabinet Secretary Yoshihide Suga flatly denied that Trump had made the Pearl Harbor remark.

“There is no such fact,” Suga told a regular news briefing Wednesday.

Contrary to his pointed denial, meanwhile, the top government spokesman was more guarded on the report’s suggestion that Kitamura had met clandestinely with the senior North Korean official.

“We’re aware of the report, but won’t comment on every single detail in it,” Suga said.