SEOUL • Officials signed a short-term agreement yesterday to boost South Korea's contribution towards the upkeep of United States troops on the peninsula, after a previous deal lapsed amid US President Donald Trump's call for the South to pay more.

About 28,500 US troops are stationed in South Korea, where the US has maintained a military presence since the 1950-1953 Korean War.

The new deal must still be approved by South Korea's Parliament, but it would boost the country's contribution to 1.03 trillion won (S$1.25 billion) from 960 billion won last year.

Unlike past agreements, which lasted for five years, this one is scheduled to expire in a year, potentially forcing both sides back to the bargaining table within months.

"It has been a very long process, but ultimately a very successful process," South Korean Foreign Minister Kang Kyung-wha said at a meeting before another official from the Foreign Ministry initialled the agreement.

While acknowledging lingering domestic criticism of the new deal and the need for parliamentary approval, Ms Kang said the response had "been positive so far".

The US State Department senior adviser for security negotiations and agreements, Mr Timothy Betts, met Ms Kang before signing the agreement on behalf of the US, and told her the money represented a small but important part of South Korea's support for the alliance.

"The United States government realises that South Korea does a lot for our alliance and for peace and stability in this region," he said.

The allies had struggled to reach a breakthrough despite 10 rounds of talks since last March, amid Mr Trump's repeated calls for a sharp increase in South Korea's contribution.

South Korea's officials have said they had sought to limit its burden to 1 trillion won and make the accord valid for at least three years.

A senior South Korean ruling party legislator said last month that negotiations were deadlocked after the US made a "sudden, unacceptable" demand that Seoul pay more than 1.4 trillion won per year.

But both sides worked to hammer out an agreement to minimise the impact on South Koreans working on US military bases, and focus on nuclear talks ahead of a second US-North Korea summit, Seoul officials said.

The disagreement had raised the prospect that Mr Trump could decide to withdraw at least some troops from South Korea, as he has done in other countries like Syria.

But South Korean officials yesterday told Yonhap news agency that the US had affirmed it would not be changing its troop presence.

Mr Trump said in his annual State of the Union address to the US Congress last Tuesday that he would meet North Korean leader Kim Jong Un on Feb 27 and 28 in Vietnam, following their unprecedented meeting in Singapore last June.

Citing officials at South Korea's presidential Blue House, Yonhap also reported that South Korean President Moon Jae-in would discuss the upcoming summit with Mr Trump "soon", and that US and North Korean officials would be meeting in an unspecified Asian country ahead of the summit.

After the June meeting, Mr Trump had announced a halt to joint military exercises with South Korea, saying they were expensive and paid for mostly by the US.

Major joint exercises have been suspended, but some small-scale drills have continued, earning rebukes from North Korea's state media in recent months.

About 70 per cent of South Korea's contribution covers the salaries of some 8,700 South Korean employees who provide administrative, technical and other services to the US military.

Late last year, the US military had warned South Korean workers on its bases they might be put on leave from mid-April if no deal was agreed.

REUTERS