South Korea and the United States signed their new pact Sunday on sharing the costs of keeping American troops in South Korea, the foreign ministry here said.

Foreign Minister Yun Byung-se and U.S. Ambassador to South Korea Sung Kim signed the renewal of the Special Measure Agreement, aimed at jointly footing the cost of stationing the 28,500 United States Forces Korea troops, according to the Ministry of Foreign Affairs.

After the signing, the pact will be submitted to the National Assembly for approval before taking effect, the ministry said.

"The latest defense cost sharing agreement is the first bilateral South Korea-U.S. alliance pact signed since the new government took office (in South Korea), and it is expected to greatly boost the South Korea-U.S. alliance and their mutual trust," the ministry's statement said.

After months of tough negotiations, the two allies struck their ninth SMA last month.

The pact, however, is likely to face some difficulties going through the parliament with some lawmakers criticizing the sharp increase in South Korea's share in the agreement.

Under the new five-year pact, South Korea is to pay 920 billion won ($858.2 million) this year, which represents a 5.8 percent increase from what it paid last year under the previous SMA.

Civic activists and lawmakers here have opposed such an increase, given the data showing that the U.S. is sitting on more than 1 trillion won of unspent defense funds paid by Seoul.

The Seoul-Washington defense treaty had initially put the burden of financing U.S. defense activities solely on the U.S. side. The allies signed their first SMA in 1991, and the deal has since been renewed intermittently.

The USFK forces are stationed in South Korea mainly as a deterrent against North Korea, a legacy of the 1950-53 Korean War. (Yonhap News)