SEOUL--South Korea reached an agreement last month to lend the United States 500,000 rounds of 155mm artillery shells that could give Washington greater flexibility to supply Ukraine with ammunition, a South Korean newspaper reported on Wednesday.

The DongA Ilbo newspaper cited unnamed government sources as saying South Korea decided to “lend” the ammunition instead of selling, to minimize the possibility of South Korean shells being used in the Ukraine conflict.

It said the shells would be used primarily by the United States to fill its stockpile.

Having bought 100,000 rounds of such shells last year, the U.S. government had asked to buy the same amount or more in February, but the South Korean government sought another way to supply the ammunition.

“We’ve opted to significantly increase the volume of shells but take the rental method, after exploring how to respond to the request of the blood ally in good faith while sticking to the government principle of not providing lethal weapons to Ukraine,” an unnamed source was quoted as saying.

Both Seoul and Washington have confirmed they were negotiating an artillery supply deal, but there has been no official word on whether an agreement was finalized.

South Korea’s defense ministry said the allies have been exploring ways to support Ukraine to help defend its freedom but declined to confirm specific discussions.

The U.S. State Department did not immediately offer comment.

Foreign Minister Park Jin told reporters that he could not confirm the newspaper report but added that the government position against providing lethal aid for Ukraine remains unchanged.

The report came after leaked highly classified U.S. military documents highlighted South Korea’s difficulties squaring pressure from western allies to help with the supply of military aid to Ukraine and its own policy of staying out of the conflict.

South Korea is a key U.S. ally and major producer of artillery ammunition but has sought to avoid antagonizing Russia in light of economic ties and Moscow’s influence over North Korea.

South Korean President Yoon Suk Yeol, who is visiting Washington this month for a summit with U.S. President Joe Biden, has said Seoul had not provided any lethal weapons to Ukraine and would expand humanitarian assistance instead.

The country’s assistance to Ukraine was included in classified documents that were leaked online earlier this year and spotlighted in reporting during the last week.

In the documents, top South Korean presidential officials worried about a plan to sell artillery shells to Washington, saying they might be diverted to Ukraine despite Seoul’s argument that the U.S. military should be the “end user.”

One leaked bulletin, marked “Top Secret” and seen by Reuters, said Seoul as of early March “grappled with the U.S. request to provide artillery ammunition to Ukraine.”

Former national security adviser 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 ultimate goals of the United States,” it said.

Another leaked document seen by Reuters, marked “Secret” and dated Feb 27, was titled “ROK 155 Delivery Timeline” and said that 153,600 rounds of 155-mm rounds could be delivered to Ukraine in about 41 days by aircraft.

Reuters was unable to independently verify the authenticity of the documents. U.S. officials have said some giving battlefield casualty estimates from Ukraine appeared to have been modified to understate Russian losses.

Seoul and Washington were scrambling to contain the fallout of the leak, saying some of the documents were altered and untrue. Kim Tae-hyo, South Korea’s deputy national security adviser, has said the two countries agreed that a “considerable number” of the released documents were fabricated.

“A third party is involved in many parts of this issue, and there is no evidence that the United States, which is our ally, has done anything to us with ill intentions,” Kim told reporters as he arrived in Washington on Tuesday to discuss Yoon’s upcoming visit.