A group of legislators visiting the United States says Washington's plan to withdraw one-third of its troops in South Korea by the end of next year may be delayed.

In a news conference in Washington, Representative Yoo Jay-kun of the ruling Uri Party quoted a senior American security official as saying the U.S. plan to pull out 12,500 troops will be finalized after negotiations between the two countries. The unidentified official was also quoted as saying Thursday that cooperation between the U.S. and South Korea has never been more active.

Rep. Yoo said U.S. officials he met expressed their hope for a peaceful resolution to North Korea's nuclear issue and for active inter-Korean economic exchanges.

Rep. Yoo arrived in Washington earlier this week, heading a delegation of the South Korea-U.S. Inter-parliamentary Exchange Council.

Earlier on Thursday, Cheong Wa Dae spokesman Kim Jong-min dismissed media reports that Washington may push back its timeframe for the troop cut, stressing that "nothing has yet been discussed between the two sides on the issue."

The speculation arose after U.S. National Security Adviser Condoleezza Rice made a one-day visit to Seoul last Friday.