Congress can block a future U.S. president from withdrawing troops from allies just as it did so when former President Jimmy Carter attempted to pull all U.S. forces out of Korea in the 1970s, a U.S. senator said.

The remark by Sen. Tom Cotton (R-AR) came as Republican presidential candidate Donald Trump has threatened to end U.S. troop presence in Korea and Japan unless the Asian allies agree to pay more for the upkeep of American forces stationed there.

"As a senator, I play an important role in crafting foreign policy. And it's important to remember that whatever the presidential candidates of either party say, they will have to interact with the United States Congress, particularly the Senate, when it comes to crafting policy," Cotton said on NBC's "Meet the Press" on Sunday.

"There's been some talk in this campaign, for instance, about our troop presence in Japan and South Korea. That's not unprecedented. Jimmy Carter proposed, when he was president, withdrawing all of our troops from South Korea. He was stopped by the United States Congress. We play an important role, and I'm going to continue to play that role, whoever is president," he said.

Concern has grown about the potential negative effects Trump could have on alliances if he is elected. The real-estate tycoon has expressed deeply negative views of alliances and U.S. security commitments overseas, seeing them as a cumbersome burden sucking up taxpayer dollars.

Trump has long argued that the U.S. should no longer be the "policeman of the world," expressing deeply negative views of U.S. security commitments overseas and claiming it makes no sense for the U.S. to help defend such wealthy allies as Japan, South Korea and Saudi Arabia in exchange for little.

He says allies should pay 100 percent of the cost of stationing American troops, or the U.S. should be prepared to end their protection. He even suggested allowing South Korea and Japan to develop their own nuclear weapons for self-defense to reduce U.S. security burdens.

About 28,500 American troops are stationed in Korea to deter North Korean aggression, a legacy of the 1950-53 Korean War, which ended in a truce, not a peace treaty. Many agree that the troop presence is also in line with U.S. interests in a region marked by China's rise. (Yonhap)