SEOUL, Oct. 18 (Yonhap) -- South Korea and the United States decided to extend their negotiations on sharing the cost of stationing American troops on the peninsula by another day in order to reach a deal, officials said Thursday.

The allies opened the eighth round of talks on the thorny issue on Tuesday for a two-day session.

In advance of the meeting, the Ministry of Foreign Affairs hinted at the possibility of stretching the talks out, as both sides are running out of time for an agreement.

The existing accord is to expire at the end of this year.

Senior diplomats of the two sides plan to meet again on Friday, according to the officials.

It's unclear whether they will be able to reach a deal this week.

One sticking point, reportedly, is Washington's call for a 50-percent increase in Seoul's contribution from the current 960 billion won (US$846 million) a year. The money is used to support the 28,500-strong U.S. Forces Korea.

Previous negotiations on the Special Measures Agreement (SMA) were held in Honolulu, Jeju, Washington D.C., Seoul and Seattle earlier this year.

South Korea's negotiating team is led by Chang Won-sam, a career diplomat who served as ambassador to Sri Lanka, and his counterpart is Timothy Betts, deputy assistant secretary of state for plans, programs and operations.

Source: Yonhap News Agency