SEOUL, South Korea — Leaked U.S. intelligence documents suggesting that Washington spied on South Korea have put the country's president in a delicate situation ahead of a state visit to the U.S., the first such trip by a South Korean leader in 12 years.

The documents contain purportedly private conversations between senior South Korean officials about Ukraine, indicating that Washington may have conducted surveillance on a key Asian ally even as the two nations publicly vowed to reinforce their alliance.

Since taking office last year, conservative President Yoon Suk Yeol has put a bolstered military partnership with the United States at the heart of his foreign policy to address intensifying North Korean nuclear threats and other challenges. The April 26 summit with President Joe Biden is seen as crucial to winning a stronger U.S. security commitment and resolving grievances over the Biden administration’s economic and technology policies.

The leaked documents were posted online as part of a major U.S. intelligence breach . The papers viewed by The Associated Press indicate that South Korea’s National Security Council “grappled” with the U.S. in early March over an American request to provide artillery ammunition to Ukraine.

The documents, which cited a signals intelligence report, said then-NSC Director Kim Sung-han suggested the possibility of selling the 330,000 rounds of 155 mm munitions to Poland, since getting the ammunition to Ukraine quickly was the United States' ultimate goal.

South Korea, a growing arms exporter, has a policy of not supplying weapons to countries at war. It has not provided arms directly to Ukraine, although it has shipped humanitarian aid and joined U.S.-led economic sanctions against Russia.

Yoon’s government said it discussed the leaked papers with the United States, and they agreed that “a considerable number” of the documents were fabricated. The South Korean government avoided any public complaints about the U.S. and did not specify which documents were faked.

“There’s no indication that the U.S., which is our ally, conducted (eavesdropping) on us with malicious intent,” Kim Tae-hyo, Seoul’s deputy national security director, told reporters Tuesday at Dulles Airport near Washington at the start of a trip aimed at preparing for the summit.

The Yoon government's stance invited criticism from liberal rivals, who called on the government to lodge strong protests with the U.S. They also suspected what they call Yoon’s hasty relocation of his presidential office to a Defense Ministry compound in central Seoul may have left the office vulnerable to wiretapping.

“As a sovereign nation, we must sternly respond to the spying of state secrets, even if it was committed by an ally" with whom South Korea has "bonded over blood,” said Park Hong-geun, floor leader of the main liberal opposition Democratic Party.

In an official statement, Yoon’s office said it maintains tight security, including anti-eavesdropping systems. It called the opposition party’s attempts to link the office relocation to the spying allegation “diplomatic suicidal acts” that shake South Korea’s national interests and its alliance with the U.S.

The situation is unlikely to threaten the country's alliance with the U.S. that was forged during the 1950-53 Korean War, many experts say.

“No big damage is expected on the Korea-U.S. alliance as it seems both governments share the view that they would focus on the alliance, more concretely on a successful state visit by Yoon,” said Bong Young-shik, an expert at Seoul’s Yonsei Institute for North Korean Studies.

If Yoon returns with some achievements, Koreans will conclude that he put up with the spying allegations "because bigger matters were at stake,” Bong said. But if the visit amounts to a ”pomp-only trip," people could question whether South Korea "made lots of concessions.”

One possible achievement for Yoon would be if South Korea takes on a role in the management of U.S. nuclear weapons in the face of North Korea’s advancing nuclear arsenal.

Other wins would be securing U.S. benefits for major South Korean businesses involved in the making of electric vehicles and easing U.S. restrictions on technology exports to China, which has been a major manufacturing base for South Korean chipmakers.

If the U.S. intends to help Yoon, "the latest incident on the documents could end up strengthening the Korea-U.S. alliance and helping South Korea win something from the U.S,” said Kim Yeol Soo, an expert at South Korea’s Korea Institute for Military Affairs.

Kim Tae-hyung, a professor at Seoul’s Soongsil University, said the exposure of possible U.S. spying could help Seoul maintain its existing policy of not supplying weapons to Ukraine. But it’s also possible that the Yoon government reconsiders that policy now that the U.S. demands are public, Kim said.

Since Russia’s invasion of Ukraine, South Korea has agreed to provide billions of dollars' worth of tanks, howitzers, fighter jets and other weapons to Poland, a NATO member.

An American official said in November that the United States had agreed to buy 100,000 artillery rounds from South Korean manufacturers to provide to Ukraine, although South Korean officials have maintained that the munitions were meant to refill depleted U.S. stocks.

Choi Jin, director of the Seoul-based Institute of Presidential Leadership, said it’s also no secret that allies spy on each other, as well as their adversaries.

The U.S. wiretapping activities “are something that everyone already knows,” although it becomes a more sensitive matter when the practice is made public, Choi said.

“I think South Koreans also try to wiretap (U.S. officials) as well,” Choi said. “People feel animosity toward the word ‘wiretapping.’ But in other words, it’s called intelligence gathering.”