Updated

South Korea's president called Tuesday for serious talks with North Korea, warning that the rivals must not repeat their "dark history" and urging Pyongyang to abandon its nuclear programs.

President Lee Myung-bak made the remarks in a nationally televised speech amid rising animosity following Monday's launch of annual South Korea-U.S. military drills, which Pyongyang calls a rehearsal for invasion. The North's state media said Tuesday that the drills could cause a "nuclear catastrophe" on the Korean peninsula.

"The Korean nation cannot afford to lag behind the currents of the times, repeating the dark history of yesteryear," Lee said, referring to the Koreas' bloody 1950-53 war and the subsequent decades of violence and tension.

Lee said South Korea could provide aid to the impoverished North and is ready to resume inter-Korean talks "anytime with an open mind." He said, however, that "the North should step forward for serious dialogue and cooperation and refrain from developing nuclear weapons and missiles."

Lee, who spoke at a ceremony marking Korea's 1919 uprising against Japanese colonial rule, also said North Korea must take responsibility for "armed provocations."

Ties between the Koreas were badly strained after North Korea shelled a front-line South Korean island in November, killing four people. The barrage came eight months after 46 sailors were killed when a South Korean warship sank. A Seoul-led international investigation blamed a North Korean torpedo attack, but Pyongyang denies involvement.

Lee's mild tone contrasted with past speeches that vowed stern and immediate retaliation against any new attacks by the North.

Earlier Tuesday, however, Lee's defense chief inspected front-line troops and ordered them to immediately return fire without reporting to him if the North attacks.

After months of high tension, North Korea had begun to call for dialogue with Seoul and express a desire to return to stalled international talks on its nuclear program. Military officers from the Koreas met last month but failed to make progress.

But anger in the North was rekindled this week when South Korea and the United States pushed ahead with annual military exercises despite North Korea's threat to retaliate.

As Lee spoke, Pyongyang's state media called the drills a dangerous plot to invade the North.

The North's main Rodong Sinmun newspaper said in a commentary that "if a war breaks out on the peninsula, only a nuclear catastrophe will be triggered."

The North's Foreign Ministry issued a statement saying the North is "ready for both dialogue and confrontation."

The military has separately warned it will fire at South Korean border towns if Seoul continues allowing activists to send propaganda leaflets to the North.

South Korean and U.S. officials have repeatedly said the drills are purely defensive.

About 12,800 U.S. troops and some 200,000 South Korean soldiers and reservists are to participate in the exercises, which are to last until late April. The training, which involves computer war games and live-firing exercises, is aimed at defending South Korea against any attack.

North and South Korea are still technically at war because their conflict ended with an armistice, not a peace treaty.