The United States is making a hard push for a much larger South Korean share in the cost of stationing American troops here than what Seoul is willing to pay, local government sources said on Sunday, casting doubt over the two sides' impending negotiations over the issue.

The two countries will open a new round of talks on Thursday in Seoul to renew the Special Measure Agreement, under which they will decide how to split the cost of stationing 28,500 U.S. troops in South Korea.

According to the sources, the U.S. is demanding South Korea contribute about 950 billion won ($900 million) under a new agreement, up 9.2 percent from 869.5 billion won that Seoul paid under the previous SMA in 2013.

South Korea believes the figure should be settled around 900 billion won, given that the annual rate of increase under the previous five-year SMA was capped at 4 percent.

Seoul is also concerned that the National Assembly will refuse to ratify the new SMA if South Korea's share exceeded 900 billion won and point out that the size of the American troops and their service conditions haven't changed so dramatically as to warrant a major increase in Seoul's cost.

When the most recent SMA was reached in 2009, the South Korean share went up by 18.5 billion won from 2008.

Sources here said the U.S. had asked for around 1.1 trillion won from South Korea early in their negotiations and demanded that the figure not fall below 950 billion won, citing mounting security threats from North Korea.

"I don't recall the U.S. being so insistent about monetary figures (in the SMA talks)," a government source said.

The sources predicted a long road ahead in the allies' talks.

"Both South Korea and the U.S. shouldn't just come to the table this time," another source said. "They must put in a lot of thoughts into this in order to reach an agreement."

Thursday's talks will be the 10th round. The previous SMA expired at the end of 2013.

The allies signed their first SMA in 1991, and the deal has been renewed intermittently since. The Seoul-Washington defense treaty, under which the U.S. deploys its soldiers in South Korea to guard against North Korean threats, had initially put the burden of financing U.S. defense activities solely on Washington. (Yonhap News)