SEOUL (Reuters) - A U.S. senator visiting South Korea has sought to reassure his hosts of the U.S. commitment to funding its military presence there, which President-elect Donald Trump had called into question during the U.S. presidential campaign.

U.S. Army M109A6 Paladin self-propelled howitzers are seen during a military exercise in Pocheon, South Korea, March 10, 2016. REUTERS/Kim Hong-Ji - RTSA4YP

South Korea is home to 28,500 U.S. troops, a legacy of the 1950-53 Korean war, and there has been concern in Seoul that a Trump administration will demand that Seoul sharply raise its share of the cost of maintaining their presence.

Sen. James Lankford, a Republican from Oklahoma, said South Korea should not worry.

“That’s a long-standing relationship between the United States and Korea. That’s something that also works its way through Congress, and both the House and the Senate have a commitment to what’s happening here,” he told Reuters in an interview on Friday.

“He (Trump) has not made a clear statement yet, as obviously he’s still trying to work through the transition into the presidency, but I have no question of his commitment to that relationship,” Lankford said.

Under a five-year cost-sharing agreement reached two years ago, Seoul agreed to contribute $867 million towards U.S. military costs in 2014, about 40 percent of the total. The deal called for the amount to rise annually at the rate of inflation.

Lankford’s visit comes amid political turmoil in South Korea, where President Park Geun-hye was impeached by parliament in a Dec. 9 vote. That vote must be upheld or overturned by the Constitutional Court, a process that could take months, during which time her powers are assumed by the prime minister.

He said his visit was intended to assure South Koreans that “the friendship is older than just any single election or any single leader”.

If Park leaves office early, an election would be held in two months. The current front-runner in polls, Moon Jae-in, said on Thursday the planned deployment of a U.S. anti-missile system should be decided by the next administration.

The Terminal High Altitude Area Defence (THAAD) system is due to be deployed in 2017 and is intended to defend against the missile threat from North Korea, which remains in a technical state of war with the South.

China vehemently opposes the THAAD deployment, concerned that its powerful radar can penetrate its territory.