South Korea's top diplomat and the new chief commander of U.S. troops in Korea on Wednesday reaffirmed their alliance in the face of persisting tensions over North Korea's nuclear and missile programs, Seoul's foreign ministry said.

Foreign Minister Yun Byung-se and United States Forces Korea Commander Vincent Brooks held talks at the ministry as the new chief of the 28,000-strong U.S. forces paid a courtesy call upon taking command late last month.

Yun congratulated Brooks on his new post and stressed the importance of maintaining and strengthening the allies' joint defense posture to immediately respond to any North Korean provocation or threat, the ministry said in a press release.

Brooks agreed with Yun, vowing to be "ready to fight tonight" in the current "grave situation" on the Korean Peninsula.

Experts believe it is a matter of time before Pyongyang carries out another provocation following its fourth nuclear test in January and long-range rocket launch in February.

Yun and Brooks discussed the need to be ready for various possibilities that may arise from North Korea's recent security threats and domestic developments, agreeing on the importance of close coordination between the allies' foreign and defense authorities, the ministry said.

The U.S. fought alongside South Korea during the 1950-53 Korean War. Since the conflict ended in an armistice, not a peace treaty, Washington has stationed troops here to deter North Korean aggression.

Yun said the alliance has been a "linchpin of peace and stability" in the region.

Brooks also serves as the commander of the United Nations Command and the Republic of Korea-U.S. Combined Forces Command. (Yonhap)