South Korea's president urged North Korea on Sunday to stop stoking tension, saying engagement with the international community will serve the reclusive communist nation's interests better than missiles and nuclear weapons.

Tension between the two Koreas has run high since conservative, pro-US President Lee Myung-bak took office in Seoul one year ago. It has further intensified in recent weeks amid reports the North plans to test-fire a long-range missile.

Pyongyang has cut off government-level talks with Seoul and halted joint projects in protest of Lee's hardline approach, which includes suspension of his liberal predecessors' policy of sending unconditional aid to the North.

"What protects North Korea is not nuclear weapons and missiles but South-North cooperation and cooperation with the international community," Lee said in a nationally televised speech marking Korea's independence movement against Japanese colonial rule.

"No one should tarnish stability and peace on the Korean Peninsula. That will never succeed."

Japanese Foreign Minister Hirofumi Nakasone, speaking after meetings Sunday with top Chinese leaders including Premier Wen Jiabao, called on the North "to exercise self-restraint and not to escalate the tension or anxiety in the region."

Chinese officials "listened to our view," Nakasone was quoted as saying in a statement read to reporters by Japanese Foreign Ministry spokesman Kazuo Kodama in Beijing. The Chinese officials had yet to "decide their judgment on their own," he said.

China remains the North's only major ally and a key donor of food and energy.

The South Korean president called for quick resumption of talks between the two Koreas, still technically at war because the 1950s Korean War ended in a truce, not a peace treaty.

"The door to unconditional dialogue is still open wide now," Lee said. "The South and North should hold a dialogue at an early date."

North Korea said last week that it was preparing to shoot a communication satellite into orbit as part of it space development program. The United States, South Korea and other neighboring countries believe the launch may be a cover for a missile test-fire, saying the action would trigger international sanctions.

Analysts say the North's planned launch is seen as a bid for President Barack Obama's attention as international disarmament talks remained stalled for months over how to verify its nuclear programs.

Obama's special representative for North Korea policy, Stephen W Bosworth, will leave on Monday for Beijing, Tokyo and Seoul for talks on the North's nuclear program and also to meet Russian officials on the matter.

The two Koreas, the US, China, Japan and Russia have been involved in on-and-off talks aimed at getting the North to give up its bombs program in return for aid and other benefits.

Lee reaffirmed South Korea is ready to help the North rebuild its shattered economy with the international community if it lives up to its pledge to abandon its nuclear weapons program.

"The denuclearization would be the shortcut for North Korea to rapidly become a member of the international community," Lee said.

Later on Sunday, dozens of conservative activists staged an anti-Pyongyang rally in Seoul, during which they burned North Korean national flags and replicas of the country's long-range missile.

"We're urging the North's nuclear dismantling," the activists chanted, raising placards reading "Down, Down with North Korea" and "Down with (North Korean leader) Kim Jong Il."