SEOUL, May 25 (Reuters) - Hundreds of thousands of South Korean artillery rounds are on their way to Ukraine via the United States, after Seoul's initial resistance toward arming Ukraine, the Wall Street Journal reported on Wednesday.

The Journal, citing unnamed sources, said Seoul had reached a "confidential arrangement" with Washington to transfer the shells to the United States to be delivered to Ukraine, after Washington asked its Asian ally last year for artillery support.

Jeon Ha-kyu, spokesman at South Korea's defence ministry, said on Thursday that it had been in talks with the Pentagon on ammunition exports but that there were "inaccurate parts" in the WSJ report, declining to give details.

"There have been various discussions and requests, and our government will take appropriate measures while comprehensively reviewing the war and humanitarian situation in Ukraine," Jeon told a briefing.

A U.S. ally and major producer of artillery ammunition, South Korea had so far ruled out sending lethal aid to Ukraine, citing business ties with Russia and Moscow's influence over North Korea, despite mounting pressure from Washington and Europe to supply weapons.

President Yoon Suk Yeol, in an interview with Reuters in April, signalled the prospect of a change, saying it might be difficult for Seoul to adhere to only providing humanitarian and financial support if Ukraine faced a large-scale civilian attack or a "situation the international community cannot condone."

The Pentagon and Yoon's office did not immediately respond to requests for comment.

When asked on Wednesday about the potential to supply ammunition to Ukraine, South Korea's national security adviser, Cho Tae-yong, told parliament that officials will make a decision after monitoring developments.

Cho said there were no plans to send shells either directly or via Poland, but did not elaborate on cooperation with the United States.

The Journal report said Seoul officials "got cold feet" following media reports on the discussions late last year, but a "breakthrough" was made after Yoon visited Washington last month for a summit with President Joe Biden.