WASHINGTON — US President Donald Trump said on Tuesday (July 8) South Korea should be paying for its own military protection and suggested the US ally needed to pay more for the US troop presence there, a day after saying he planned to impose a 25 per cent tariff on its imports.

"It's very unfair. We supply the militaries to many very successful countries," Trump told reporters at a meeting of his Cabinet at the White House.

"South Korea is making a lot of money, and they're very good. They're very good, but, you know, they should be paying for their own military."

Trump said at he had got South Korea to agree to pay more for the presence of US forces during his first term, but his predecessor Joe Biden "cancelled" the deal.

"I said to South Korea... you know, we give you free military, essentially, very little," Trump said, adding that he had told them they should pay US$10 billion (S$12.8 billion) a year.

"I got three (billion) with a phone call... but I said next year we have to talk," he said, making claims Reuters has not verified.

Trump said the presence of US forces was a "huge" economic benefit for countries that hosted them.

"It's like having a city, it's tremendous money for them, and it's a tremendous loss for us... so we're talking, in a very nice way, We're talking to them."

South Korea hosts about 28,500 American troops as a legacy of the 1950-1953 Korean War. It relies on the US nuclear umbrella for protection against China, Russia and North Korea, and is seen as a key ally for projecting US military power.

Shortly before last year's US election, South Korea and the Biden administration hurried to sign a new, five-year agreement under which Seoul would raise its contribution toward the upkeep of US troops by 8.3 per cent to US$1.47 billion in the first year, with later increases linked to the consumer price index.

During his election campaign Trump said South Korea should pay as much as US$10 billion per year, and has said such costs would be part of trade negotiations.

Trump in the past has suggested he could withdraw US forces stationed overseas if countries did not pay more for their upkeep.

In May, the Pentagon said a Wall Street Journal report that the US was considering withdrawing roughly 4,500 troops from South Korea was not true.

Source: Reuters