South Korea and the United States held a new round of negotiations Tuesday on sharing the cost for the upkeep of the 28,500-strong US Forces Korea, Seoul's foreign ministry officials said.

The three-day talks in Seoul came about two weeks after South Korea's chief negotiator Lee Tae-woo and his U.S. counterpart, Linda Specht, held the third round of negotiations on the Special Measures Agreement (SMA) in Washington.

Tuesday's talks lasted for about seven hours until 5 p.m.

"Now that the two sides have identified each other's basic stance, I believe we're entering a phase of (negotiating) in detail, by sector," a Seoul official said on condition of anonymity.

The allies launched the negotiations in April, earlier than expected, amid speculation that Seoul wants an early deal to avoid tough bargaining with Washington in case former US President Donald Trump returns to the White House.

Under Trump's presidency, Washington had demanded more than a fivefold increase in Seoul's payment to $5 billion.

The current six-year SMA, due to expire at the end of next year, committed South Korea to paying $1.03 billion for 2021, a 13.9 percent increase from 2019, and increasing the payment every year for the subsequent four years in line with the rise in Seoul's defense spending.

South Korea has said it seeks to have negotiations based on the position that its share should come at a "reasonable level," to create an environment for the stable stationing of the U.S. Forces Korea and to strengthen the allies' combined defense posture.

Since 1991, Seoul has partially shared the cost for Korean USFK workers; the construction of military installations, such as barracks, as well as training, educational, operational and communications facilities; and other logistical support. (Yonhap)