The U.S. ambassador to South Korea voiced optimism Tuesday about the future alliance between the two countries, saying that Seoul-Washington ties will be further bolstered whoever wins the December presidential election here.

U.S. President Barack Obama won re-election and South Koreans go to the polls on Dec. 19 to pick their next leader. Some South Koreans are concerned that the current lockstep cooperation between the two countries is unlikely to be sustainable, particularly for the North Korea policy, if a liberal candidate wins.

"One thing that will not change is our commitment to the special partnership between our two countries," U.S. Ambassador Sung Kim said at an annual meeting hosted by the Korean-American Association.

"I also optimistic about the future of our partnership because of hard works and dedication" by the two nations," he said.

The ambassador hailed the alliance between South Korea and the U.S. is a linchpin of stability in Northeast Asia. "We take seriously our mission of maintaining peace and stability on the Korean Peninsula," he said.

In South Korea, public polls show that the forthcoming presidential election would be a close call, with ruling party candidate Park Geun-hye running neck-and-neck in hypothetical two-way races with her main rivals, main opposition candidate Moon Jae-in and independent candidate Ahn Cheol-soo.

South Korean President Lee Myung-bak's single five-year term ends in February 2013. By law, he cannot seek re-election. (Yonhap News)