U.S. soldiers during Warrior Strike VIII, a bilateral training exercise between the U.S. Army’s 2nd Armored Brigade Combat Team, 1st Cavalry Division, and the South Korean army in Paju, South Korea, on Sept. 19, 2017. (SeongJoon Cho/Bloomberg News)

President Trump’s demands that South Korea take on far more costs for hosting U.S. troops is straining the alliance and potentially playing into North Korea’s hands ahead of a second summit with Kim Jong Un, South Korean lawmakers and experts say.

South Korea has about 28,500 U.S. troops on more than 20 sites and paid $855 million last year toward the cost. But the cost-sharing pact expired at the end of last year after 10 rounds of negotiations that left — in the words of one Foreign Ministry official in Seoul — a “huge gap” between both sides.

South Korean lawmakers and experts worry that Trump is so obsessed with Seoul paying more that he could take the previously unthinkable step of withdrawing some troops if a deal is not reached. 

That would be an indirect gift to Kim, undermining one of the most important cards the United States has during negotiations over North Korea’s nuclear program, experts say.

The White House said Friday that Trump and Kim would meet in late February. The location was not immediately announced. Trump met earlier for about 90 minutes in the Oval Office with Kim Yong Chol, a former spy chief who has served as Pyongyang’s lead negotiator.

“We are experiencing difficulties because the U.S. side abruptly brought up a condition totally unacceptable to our side at the last stage of negotiations,” Chung Eui-yong, national security adviser to South Korean President Moon Jae-in, told reporters last week.

Chung said he still believed that the two sides could reach a “reasonable deal,” and many experts expect a crisis to be averted.

But there is no doubt the risks are growing, especially if a deal isn’t reached before Trump’s potential summit with the North Korean leader.

“I am very concerned,” said Chun Yung-woo, a conservative former national security adviser. “The danger of failure of the negotiations is, I think, broadly underestimated.”

Lawmakers from the Foreign Affairs and Unification Committee, which need to approve any deal and have been briefed on the negotiations, said the United States first demanded South Korea nearly double its contribution, to $1.6 billion, but later scaled that back to $1.2 billion.

When that demand was also rejected, Washington lowered the money demands but suggested the deal be extended for only one year, instead of the usual five.

The United States has also proposed that South Korea cover some “operational costs” for the U.S. military presence in the region, including deploying aircraft carriers. South Korean lawmakers called this demand unacceptable.

Lawmakers from both the liberal ruling party and conservative opposition said South Korean public opinion is sensitive to any impression that the United States is bullying them. Moon’s government, meanwhile, cannot afford to look weak in the eyes of its own people.

“One trillion won is a psychological barrier,” said Lee Soo-hyuck, a ruling-party lawmaker, referring to an amount in South Korean won equivalent to nearly $890 million.

“It would be very difficult to get the consent of the National Assembly if it is over 1 trillion,” Lee added. “We would need some very persuasive argument or logic.”

Ruling-party lawmaker Song Young-gil called Trump’s demands “unreasonable and groundless,” while Won Yoo-chul, a conservative member of the foreign affairs committee, fears a backlash that will fuel “anti-American sentiments among the Korean people.”

Timothy Betts, the U.S. deputy assistant secretary of state for plans, programs and operations, is leading negotiations. But instructions appear to be coming directly from the White House.

Trump has said the United States gets “practically nothing” toward the cost of the troops, while complaining bitterly about South Korea’s trade surplus with the United States — until the two sides signed a new trade deal in September.

In “Fear,” Bob Woodward’s account of the Trump White House, the president is described as being obsessed with the cost of the U.S. troop presence, angrily threatening to pull them out on more than one occasion. 

At various times, he was talked down by a host of insiders, including Defense Secretary Jim Mattis, Secretary of State Rex Tillerson and Gen. Joseph F. Dunford Jr., chairman of the Joint Chiefs of Staff.

Today, only Dunford remains in his job, with Mattis’s resignation — over the plan to withdraw troops from Syria and the treatment of U.S. allies in general — seen as especially damaging.

“It'll make it much harder,” said Victor Cha, a senior adviser at the Center for Strategic and International Studies. “There'll be nothing to filter what Trump wants to do, nothing to filter a very uniformed view on how he wants things done.”

Cha said the Trump administration is looking for a “paradigm shift” in military burden sharing and is particularly keen to establish a precedent with South Korea ahead of similar negotiations with Japan and NATO next year.

Many members of the Moon administration began their political careers as left-wing pro-democracy student activists, who were inclined to see the U.S. troop presence as more motivated by American strategic interests than South Korea’s views.

“I don’t think they will ever ask the U.S. to withdraw,” said Chun, the conservative former national security adviser, referring to officials in Moon’s entourage. “But if President Trump decides to withdraw because of this cost issue, I don’t think any of them will cry over that kind of decision.”

The question of the share South Korea is paying depends on your vantage point.

The United States says Seoul pays $855 million out of a total cost of about $2 billion. South Korea says that doesn’t account for the large amount of land supplied rent-free and calculates it pays more like 70 percent of the cost. 

Seoul also paid almost the entire cost of building a massive new U.S. base at Pyeongtaek and spent $13 billion between 2013 and 2017 on U.S. military hardware, training and services.

Talks have overrun the deadline before. After the last agreement expired in December 2013, a new deal wasn’t implemented until the following June. 

But Kim Jong-dae, a lawmaker with the left-leaning Justice Party, said the risks are higher this time, given Trump’s “isolationist” tendencies and clear desire to bring more U.S. soldiers home.

Many South Koreans, he said, were pleasantly surprised by Trump’s sincere attempt to make peace on the Korean Peninsula but are perplexed by his “coldhearted dealmaking” over the troop-cost issue.

In Pyongyang, though, Kim Jong Un is probably happy at any hint of a possible reduction in U.S. forces.

“The withdrawal of U.S. troops is the most important card to play in getting North Korea to denuclearize,” Chun said. “What I am most concerned about is that [Trump] will waste the card without using it. If he decides to withdraw troops out of exasperation without thinking of how to link to denuclearization negotiations, this becomes a dead card.”  

Min Joo Kim contributed to this report.