WASHINGTON (REUTERS) - US President Donald Trump said on Wednesday (Aug 7) discussions have begun with South Korea, aimed at getting the country to pay more for the cost of maintaining US troops in the region to guard against any threat from North Korea.

"Talks have begun to further increase payments to the United States. South Korea is a very wealthy nation that now feels an obligation to contribute to the military defense provided by the United States of America," Mr Trump said in a Twitter post.

South Korea's presidential Blue House did not immediately respond to request for comment on the talks.

Mr Trump has repeatedly said Seoul should bear more of the burden of keeping some 28,500 US troops stationed in South Korea, where the United States has had a military presence since the 1950-53 Korean War.

South Korean and US officials signed an agreement in February, under which Seoul would raise its contribution to just under 1.04 trillion won (S$1.3 billion), an increase of about S$97 million. The interim agreement was due to expire in a year.

US national security adviser John Bolton discussed the cost-sharing issue during his visit to Seoul in July, according to the Blue House.

Mr Trump's tweet comes ahead of US Secretary of Defense Mark Esper's first official visit to Seoul as part of a tour through Asia in August.

US and South Korean militaries are planning to stage a joint exercise this month as well.