"No, it's not. That is not one of the things on the table," Trump said when asked if he would consider pulling some of the 28,500 troops from South Korea.

Trump, answering questions as he met at the White House with a senior Chinese official, said that he would not reveal his bargaining cards ahead of next week's summit in Hanoi.

Pressed on what he would offer, Trump quipped: "Everything is on the table."

Trump again hailed his relations with North Korean leader Kim Jong Un, whom he met in June in Singapore in the first-ever summit between the two adversaries.

The US leader will face pressure to produce more concrete results when they meet over two days at their second summit.

The businessman turned president has long mused about withdrawing US troops from allies, seeing them as an expense shouldered by the United States by countries that are often commercial competitors.

Heightening speculation that troops could be on the table, the United States and South Korea have been struggling to finalize a new arrangement on how much Seoul will pay for the US military presence, with the Trump administration pressing for more.

North Korea has never formally ended the 1950-53 war with its neighbor and officially is seeking reunification with the South.

But any bid to remove US troops would face strong pushback from the US Congress and Japan, whose conservative government is deeply wary of North Korea's intentions.

And South Korean President Moon Jae-in has shown little interest in booting out US troops, in contrast with some of his predecessors who shared his left-of-center ideology.