The national security advisor under former U.S. President Bill Clinton says the Bush administration's decision to cut 12,000 soldiers from its troop presence in South Korea is spawning serious concerns in some political circles.

In a seminar held in Washington on the theme of 'Northeast Asian regionalism and the Seoul-Washington alliance,' Sandy Berger said that considering the current instabilities on the Korean peninsula, Washington needs to assure its Korean ally that the U.S. is serious about Seoul's security.

Professor Francis Fukuyama of Johns Hopkins University, who also attended the seminar, pointed out that the hitherto rock-solid alliance of the two nations is not guaranteed to remain the same, citing changing perceptions among young Koreans and the planned re-alignment of the U.S. troop presence in South Korea.