SEOUL, South Korea (AP) — Leaked US 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 US, 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 US 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 US intelligence breach. The papers viewed by the Associated Press indicate that South Korea’s National Security Council “grappled” with the US 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 US-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 US and did not specify which documents were faked.

“There’s no indication that the US, 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 White House did not immediately respond to a request for comment.

The Yoon government’s stance invited criticism from liberal rivals, who called on the government to lodge strong protests with the US. They also suspected what they call Yoon’s hasty relocation of his presidential office to a Defence 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 US.

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

“No big damage is expected on the Korea-US 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.