South Korean President Yoon Suk-yeol says he will seek tangible outcomes on dealing with North Korea in his upcoming summit with US President Joe Biden. The North has been ramping up its nuclear and missile development.

Yoon spoke in an interview with Reuters news agency ahead of his state visit to the US next week.

Yoon stressed that his government will upgrade deterrence against the North by strengthening its surveillance, reconnaissance and intelligence analysis capabilities, and developing new weapons.

On the issue of Ukraine, Yoon said if there is a situation the international community cannot condone, such as a large-scale attack on civilians or a massacre, it might be difficult for South Korea to insist only on humanitarian or financial support.

Yoon's remark could signal a shift in the South Korean government's refusal to provide lethal weapons to Ukraine.

But South Korea's public broadcaster KBS quoted a source at the presidential office as saying that there is a low possibility of such a shift at this point.

In Moscow, Russian presidential office spokesperson Dmitry Peskov told reporters on Wednesday that unfortunately, Seoul has taken quite an unfriendly position in terms of sanctions and other things, and this is a continuation.

Peskov said the start of arms deliveries to Ukraine "would imply a certain involvement in this conflict."