South Korea said its military forces remained on alert Sunday a day after North Korea issued a statement pledging "an all-out confrontational posture."

The Korean People's Army called South Korea's president a "traitor" and accused him of preparing a military provocation, according to a Saturday report by the North's state-run Korean Central News Agency.

A Defense Ministry official said Sunday the South's military will remain on alert. The official spoke on condition of anonymity citing department policy.

The North has issued similar threats in the past in anger over hard-line policies that South Korean President Lee Myung-bak has implemented since taking office last year.

South Korea denies taking a confrontational stance and has repeatedly called for dialogue with the North.

Koh Yu-hwan, a North Korea expert at Seoul's Dongguk University, said the North's latest saber-rattling could be a negotiating tactic aimed at Seoul and Washington ahead of the Tuesday inauguration of President-elect Barack Obama.

South Korea, the U.S. and three other nations have sought to coax North Korea — which detonated an atomic device in 2006 — to give up its nuclear program by offering aid for disarmament. The pact has been deadlocked over how to verify North Korea's past nuclear activities.

An American nuclear expert said Saturday following a trip to the North that Pyongyang told him it has "weaponized" 67.8 pounds of plutonium into warheads.

That much plutonium would produce four to five warheads, depending on the grade of plutonium, the specific weapons design and the desired explosive yield, said Selig Harrison, director of the Washington-based Center for International Policy's Asia program.

The two Koreas have been separated by troops, tanks and one of the world's most heavily armed borders since a three-year war ended in a truce in 1953.