The U.S. will lose much of its leverage in Asia if it pulls troops out of South Korea, a U.S. congressman said Friday, criticizing Donald Trump's suggestion that the U.S. should end defense support for allies unless they pay more.

"If we pull out of the Pacific and we, you know, take our troops out of Korea and take our troops out of Japan, then we lose much of the leverage," Rep. Peter King (R-NY) said on CNN. "It certainly, you know, it weakens the leverage we have against China and it, in effect, makes China more a Pacific power than we are right now."

In a major foreign policy speech earlier this week, Trump said that allies are not paying their fair share for U.S. defense support, and the U.S. must be prepared to "let these countries defend themselves" unless they foot more of the bill for the defense.

The real-estate tycoon has long made the case, but the address was seen as carrying more weight than before because it was the first time Trump has outlined his foreign policy priorities in such a formal and refined manner.

Though Trump made no mention of South Korea, the remark suggested that if elected, he could seek to pull 28,500 American troops from the Asian ally unless Seoul agrees to pay more.

King pointed out that South Korea already shoulders much of the cost for the upkeep of U.S. troops.

"Right now, they are picking up a large percentage of it. And it is cheaper for us to keep troops in Japan and Korea than it is to have them back here in the United States. So, it is saving the U.S. money by having troops in Japan and Korea," he said.

"But if we want to negotiate a slightly higher amount, that's one thing. But the fact is that amount has gone up in the past. And right now, again, it saves the U.S. money by having our troops stationed in those two countries," he added.

In 2014, the two countries renewed their cost-sharing agreement, known as the Special Measures Agreement, with Seoul agreeing to pay 920 billion won (US$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.

Earlier this month, Gen. Vincent Brooks, the incoming commander of U.S. Forces Korea, said that Seoul is shouldering a "significant load" of the costs for the stationing of American troops in the country. He also said it would cost more to keep those troops stationed in the U.S. than it does in Korea. (Yonhap)