PYEONGTAEK (South Korea) • US forces in South Korea have opened their new headquarters on what they called Washington's biggest overseas base, just weeks after President Donald Trump said he wanted to bring the troops home.

The US and South Korea are treaty allies and for decades US Forces Korea (USFK) have been headquartered in Yongsan, located in the centre of Seoul.

The two allies agreed as long ago as 1990 to relocate the headquarters to Camp Humphreys, an existing base in Pyeongtaek about 60km south of the capital. But the project was delayed for years by resident protests, financial issues and extensive construction work.

The USFK headquarters moved yesterday, as did the US-led United Nations Command, under whose flag the allies fought in the Korean War, with more units to follow suit later.

The US has 28,500 troops stationed in the South to defend it from the nuclear-armed North, and the move came only weeks after Mr Trump announced after his unprecedented summit with North Korean leader Kim Jong Un that he would suspend joint military exercises with the South.

Mr Trump has demanded that the South pay more towards the US military presence in the country, and negotiations on the issue are continuing.

But USFK commander Vincent Brooks told yesterday's opening ceremony that Seoul had contributed more than 90 per cent of the US$10.8 billion (S$14.7 billion) cost of Camp Humphreys.

Camp Humphreys has a total of 513 buildings including schools, shops and banks spread over more than 14.7 million sq m. It will accommodate 43,000 people including soldiers and their family members by the end of 2022.

South Korea's defence minister Song Young-moo said the USFK would embrace a new role as circumstances shifted "from Cold War confrontation to peaceful co-existence".

He added that it would "contribute not only to peace on the peninsula but also to world peace as a stabiliser in North-east Asia".

AGENCE FRANCE-PRESSE