SEOUL - South Korean President Lee Myung-bak called on North Korea's new leader to seize the opportunity and return to dialogue, saying he was prepared to offer help to revive the North's shattered economy if it suspends nuclear activities.Two days after a state funeral for Kim Jong-il, North Korea sounded a bellicose note against the South on Friday, assailing Lee's government for lacking the decency to mourn the death of a compatriot leader and vowing to continue a hardline policy.The North's new leader, Kim Jong-un, toured a major army tank division on Sunday in his first public activity as supreme commander, underlining that he would stick to his father's songun, or military-first, policy."We have left the window of opportunity open," Lee said in a New Year address broadcast from South Korea's presidential Blue House. "If North Korea comes forward with sincerity, we will be able to open a new era for the Korean peninsula together."As soon as North Korea suspends nuclear activities in progress, six party talks should be able to resume. Through a six-party agreement, we are prepared to ease the North's security concern and provide necessary resources to revive its economy."The six party talks, involving the two Koreas, the United States, Japan, Russia and China, have been stalled since 2008 when the North walked away from an aid-for-disarmament deal.Experts who study the North said it was unlikely it would take a dramatically different path under its new ruler, who at around 27 is believed to lack the experience or political support to initiate his own line of policy.In a New Year message issued in its state newspapers that normally sets out policy for the year, the North made no mention of its nuclear programs which had been the key source of regional security worry during Kim Jong-il's reign.Under Kim Jong-il's leadership, the reclusive state twice tested nuclear devices, as well as variety of missiles. Experts say, however, the North still lacks the ability to miniaturize a nuclear bomb to fix atop a missile.The untested new leader is the third member of the Kim dynasty to rule but he had only been groomed for power since 2009.Analysts believe he will rule with the aid of a close coterie that includes his uncle and key power-broker, Jang Song-thaek, at least in the early stages of the leadership transition.North Korea has called for the resumption of the nuclear talks, but Washington and Seoul have been reluctant to rush back to the table, wary of Pyongyang's potential to engage in protracted negotiations only to walk away from its obligations.Most analysts say the North will never give up its nuclear weapons program, as it provides the authoritarian state with the ultimate deterrent as well as a bargaining chip in negotiations.Tension has eased over the past year after escalating to its highest level in decades in 2010 when 50 South Koreans were killed in two separate attacks.Lee said the South would retaliate against any aggression by the North but he said he had hoped there would be progress on ending its nuclear program.