SEOUL, South Korea (AP) - South Korea's president is urging rival North Korea to use the transition of leadership after Kim Jong Il's death to usher in a new era of peace on the tense Korean peninsula, even as he warned the North against any provocations.

President Lee Myung-bak reached out in his New Year's message Monday to the North Korean government now led by Kim's son, Kim Jong Un, saying he has high hopes for a breakthrough this year in negotiations over the North's nuclear program.

However, Lee warned that Seoul would respond sternly to any North Korean provocations. Relations between the rival Koreas dropped to their lowest point in decades following the 2010 sinking of a South Korean warship that killed 46 sailors and North Korea's deadly shelling of a front-line island later that year.

Lee's comments in a nationally televised speech came a day after the North called on its citizens to rally around Kim Jong Un and transform themselves into his "human shields."

Lee said Kim Jong Il's death is "portending a sea change" for the fractured Korean peninsula.

The Korean peninsula remains in a technical state of conflict because the 1950-53 Korean War ended in a truce, not a peace treaty. The Koreas remain divided by a heavily fortified border.