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."