Russia's invasion of Ukraine could further increase North Korea's reluctance to abandon nuclear arms, former US Forces Korea (USFK) chiefs have said, raising the need for Seoul and Washington to beef up their combined readiness.

In its monthly newsletter, the Korea-US Alliance Foundation (KUSAF) released a summary of their recent comments on the Ukraine crisis and its ramifications on the Korean Peninsula without identifying them.

Their comments came amid a view that Russia's attack on the pro-West country last week could be a foretaste of what a weak nation could face in a world of power politics.

"The Ukraine situation could further solidify the North's determination against abandoning nuclear arms," the USFK commanders were quoted by KUSAF as saying.

The commanders also said that the Ukraine crisis could be an opportune time for "mischief," stressing the need for South Korea and the US to strengthen their combined training and intelligence capabilities.

For the North, the armed conflict in Ukraine could offer a lesson for modern-day warfare combining cyber incursions, information warfare and other maneuvers that proceed under multi-domain operations.

But the commanders forecast the current situation in Ukraine will not directly affect the security of the peninsula, while offering a reassuring message: The US support for South Korea in a contingency will not weaken.

"Rather, (the US') response to North Korean threats will be swift and sturdy," they said.

The North, meanwhile, fired a ballistic missile on Sunday, marking its eighth missile launch since the start of the year.

The test came amid concerns the North could fire a long-range rocket under the disguise of a satellite launch or conduct other provocative acts following its veiled threat last month to suspend its voluntary moratorium on nuclear and intercontinental ballistic missile tests. (Yonhap)