The Republican spoke with Prime Minister Han Duck-soo, who is acting as president of South Korea since former leader Yoon Suk Yeol was removed from office for attempting to subvert civilian rule.

"We talked about their tremendous and unsustainable Surplus, Tariffs, Shipbuilding, large scale purchase of U.S. LNG, their joint venture in an Alaska Pipeline, and payment for the big time Military Protection we provide to South Korea," he wrote on his Truth Social platform.

Trump said they had "the confines and probability of a great DEAL for both countries," though he did not specify on which issue.

He said that a "top team" from South Korea was en route to the United States for further talks, and "things are looking good."

Last week Trump announced sweeping and punitive tariffs against the United States' biggest trading partners, the most severe of which are due to come into force on Wednesday.

Goods from South Korea are set to be taxed at 25 percent.

The tariffs announcement has rocked global stock markets, with investors uncertain over whether they are a negotiating tactic or permanent US position.

Trump has insisted he will not back down until he has reduced or even wiped out US trade deficits -- while simultaneously signalling that he is ready to negotiate with countries around the world.

Administration officials have "received the instruction to prioritize our allies and our trading partners like Japan and Korea and others," White House economic advisor Kevin Hassett told Fox News on Tuesday.

On Truth Social, Trump said his administration also plans to bring up "other subjects" with countries that are not covered by trade, and negotiate them also.

China -- which has come in for among the most severe tariffs -- "wants to make a deal, badly, but they don't know how to get it started. We are waiting for their call. It will happen!" Trump wrote.

In 2024, the US trade deficit with South Korea amounted to just over $66 billion in goods.