By Jung Sung-ki
Staff Reporter

A South Korea-U.S. military exercise, which begins today, may complicate the release of four South Korean fishermen who have been detained in North Korea for over two weeks, observers here said Sunday.

The fishing boat "800 Yeonan" strayed into North Korean waters on July 30 due to a reported mechanical failure.

The 10-day Ulchi Freedom Guardian (UFG) exercise comes at a time when North Korea has made an attempt to improve relations with the United States and South Korea, following the release of two American journalists after former U.S. President Bill Clinton made a surprise visit to the communist state.

The exercise also comes after Hyundai Group Chairwoman Hyun Jung-eun crossed the inter-Korean border to win the release of a Hyundai employee who had been detained since March. The worker, Yu Seong-jin, was freed and returned home, Thursday.

In his speech marking the Aug. 15 Liberation Day, President Lee Myung-bak offered a promise to provide aid to North Korea if it gives up its nuclear program.

Pyongyang criticized the joint training exercise by South Korean and U.S. forces, calling it a rehearsal for invasion.

"The maneuvers for a nuclear war projected by the U.S. imperialists and the Lee group of traitors are by no means a demonstration of military muscle of a defensive nature," a spokesman for the Panmunjeom Mission of the (North) Korean People's Army said in a statement. "Through this nuclear war exercise, the American master and his servant seek to openly call for escalating their sanctions and pressure upon the DPRK."

gallantjung@koreatimes.co.kr