Jeong is the first South Korean official selected from the financial realm to lead the cost-sharing negotiations. Up until now, the position has been taken by officials from either the foreign or defense ministries.

The appointment of a financial expert suggests Seoul would not easily back down in the face of US demands. 

Jeong will replace Chang Won-sam, who negotiated the current deal and represented South Korea during this week's first round of negotiations, as the government has been in the process of selecting his successor.

James DeHart, a former charge d'affaires of the US Embassy in Norway, led the US delegation.

US has demanded Seoul pay more for the US troop presence.

Under this year's SMA, South Korea agreed to pay 1.04 trillion won ($867 million), an increase of 8.2 percent from the previous year.

Wrapping up the first round of the talks on Wednesday, the two sides agreed to work toward a "reasonable and fair" sharing of the cost, according to the ministry.

An official said it would not be easy to seal the deal within this year.

"I don't think closing the deal in three months would be easy.

A lot of effort will be needed to clinch the agreement," a foreign ministry official said.

This year's deal was reached in February.

The allies could face off over not only the amount that Seoul will pay but also other contentious issues, such as the duration of the new SMA and other specific items to be covered by the deal, according to observers.   

Since 1991, Seoul has shouldered partial costs under the SMA -- for Korean civilians hired by the USFK, the construction of military facilities to maintain the allies' readiness and other forms of support. (Yonhap)