South Korea sees an opportunity for better relations with North Korea as its new leader takes power, President Lee Myung-Bak said on Monday, while vowing to respond strongly to any provocations.
"Our biggest goal is the peace and stability of the Korean peninsula," Lee said in a televised New Year address. "We are leaving the window of opportunity open."
Lee said the peninsula's political situation "is at a new turning point. But there are new opportunities in the changes and uncertainties," he added.
"We will be able to open the door for a new era in the Korean peninsula if North Korea shows sincerity."
The North has harshly criticised the South's conservative president since its longtime leader Kim Jong-Il died on December 17 and his son Jong-Un took power.
On Friday, Pyongyang's top decision-making body, the National Defence Commission, warned the world to expect no policy changes under the son.
It threatened unspecified retaliation against the South for perceived disrespect during the mourning period for the late leader.
The South "will thoroughly maintain national security as long as there is a possibility of provocation by the North", Lee said. "We will respond strongly if provoked."
The president said he expected "big changes" following Kim's death and hoped 2012 would be a turning point in years-long efforts to negotiate an end to the North's nuclear programmes.
Six-party negotiations could resume as soon as Pyongyang halted its atomic activities, he said.
Cross-border ties have been frosty since Lee took office in February 2008 and scrapped his liberal predecessors' policy of near-unconditional aid and engagement with the North.
Relations turned icy when the South accused the North of torpedoing a warship in March 2010 with the loss of 46 lives.
The North denied involvement but killed four South Koreans in an artillery attack on a border island in November 2010.
On Sunday, in a state newspaper editorial setting policy for 2012, Pyongyang stressed continuity as the untested Jong-Un, aged in his late 20s, takes over from the longtime leader.
Its urged its military to become "human rifles and bombs" to defend Jong-Un and to rally behind him.
The North Friday had vowed never to deal with Lee's government. It renewed the attack Saturday, threatening to "settle accounts" unless Seoul apologises for the alleged insults.
"He is the worst type of anti-reunification element, traitor and pro-US fascist maniac steeped in extreme bitterness towards compatriots and confrontation hysteria to the marrow of his bones," the state Committee for the Peaceful Reunification of Korea said.
Sunday's editorial renewed criticism of Lee, who is in his last full year in office.
Seoul expressed sympathy to the North's people but not its regime and allowed just two private mourning delegations to visit Pyongyang. It did not send an official delegation.
The South's unification ministry said Monday it is ready anytime to hold dialogue with the North and cooperate to ensure peace and stability.