U.S. Republican presidential front-runner Donald Trump on Monday repeated his unfounded criticism that South Korea is being defended by the United States while paying little for the upkeep of American troops stationed in the Asian ally.

"South Korea is very rich, great industrial country, and yet we're not reimbursed fairly for what we do," Trump said at a meeting with The Washington Post's editorial board. "We're constantly sending our ships, sending our planes, doing our war games; we're reimbursed a fraction of what this is all costing."

Trump also said he does not think the U.S. benefits from its involvement in the region.

"I think we were a very powerful, very wealthy country, and we are a poor country now. We're a debtor nation," he said, according to The Post.

About 28,500 American troops are stationed in South Korea to deter North Korean aggression, a legacy of the 1950-53 Korean War that ended in a truce, not a peace treaty, leaving the divided peninsula still technically at war.

Seoul has long shared the cost of stationing U.S. forces.

In 2014, the two countries renewed their cost-sharing agreement, known as the Special Measures Agreement, with Seoul agreeing to pay 920 billion won ($886 million) for the upkeep of the U.S. troops in 2014, a 5.8 percent increase from a year earlier.

Moreover, the American military presence on the peninsula is seen as in line with U.S. national interests in a region marked by a rising China. (Yonhap)