Trump says N Korea's Kim has responded to his request for a conversation

United States President Donald Trump says North Korean leader Kim Jong Un has responded to his recent outreach, a day after ordering the Pentagon to scale back drills with longstanding ally South Korea.

When asked by reporters at the Oval Office on Monday why Kim had not responded to his request for a conversation, Trump replied, "How do you know he hasn't responded?"

Pressed again, Trump said, "Yeah, he has."

The US president went on to describe the exchange as "very positive", without providing further detail.

There was no immediate comment from North Korea.

Trump on Sunday instructed the Pentagon to "substantially reduce" joint military exercises with long-term Asian ally South Korea.

Writing on his Truth Social platform, Trump said the annual drills were "not only costly ... but send a signal that is totally inappropriate and hostile, to a Country that, as long as Donald J. Trump has been President, has been unthreatening and respectful".

He also linked the decision to Seoul's refusal to help with the US-Israel war on Iran.

"Wait a minute," he said at the Oval Office. "We have 39,000 soldiers over there, guarding you from Kim Jong Un, your next-door neighbour, and you're not going to help us on a very easy military operation in Iran. That's strange."

South Korean officials said the exercises had begun as planned and that they hoped the personal chemistry between Trump and Kim would bring them back to talks.

On Tuesday, Seoul's presidential office said the drills did not reflect "any intention to attack North Korea or escalate tensions on the Korean peninsula".

South Korean President Lee Jae Myung reiterated that their fundamental purpose is "not to treat a specific entity as an adversary, but to safeguard the safe and peaceful daily lives of the people", his office added.

Since Trump and Kim last met in 2019, North Korea has significantly strengthened ties with Russia while maintaining close relations with China.

Trump's administration has repeatedly criticised North Korea's military support for Russia in Ukraine, but on Monday the US president said "Kim Jong Un has always treated me with great respect.

"I understand him. He understands me," he said.

Victor Cha, head of the Korea programme at Washington's Center for Strategic and International Studies think tank, doubted North Korea would respond immediately.

"I think they're going to bide their time and wait a little bit," he told the Reuters news agency.