Regional powers agree that there is no other choice but to put more pressure on North Korea to bring the North back to denuclearization talks, a senior South Korean official said Monday.

Realistically, however, there could be different views on the specific ways and level of pressure, he said on background.

It represents a dilemma for South Korea, which is seeking to get tougher on its increasingly hostile communist neighbor.

The South's top nuclear envoy, Hwang Joon-kook, held trilateral discussions with his U.S. and Japanese counterparts, Sung Kim and Junichi Ihara, in Seoul last week. Hwang and Kim then visited Beijing for separate talks with China's top diplomat on Korea, Wu Dawei.

The series of diplomatic meetings came in response to Pyongyang's claims of launching a ballistic missile from a submarine and mastering a technology to mount nuclear bombs onto missiles.

In Tokyo, senior officials from South Korea, the U.S., Japan, China and Russia met for a regional security forum. All the countries are members of the now-suspended six-party talks on the North's nuclear weapons program.

"The five parties have agreed on the need for pressure on North Korea. For now, there is no option other than pressure," the official told reporters on the condition of anonymity. "But there could be differences on what and how to do."

Besides U.N.-led sanctions, the human rights issue can be a card to ratchet up pressure on the North, but China and Russia remain opposed to that, he pointed out.

"Economic cooperation can also serve as a tool for pressure," the official said, but he stopped short of elaborating.

What is important is to "change the thought and calculation" of the North's leaders and persuade Pyongyang to return to the negotiating table, he added.

Pyongyang has not budged at all, passing the responsibility for lack of dialogue to Washington.

In a statement issued Sunday, the North's foreign ministry said it's too late for any talks, saying the country will continue its efforts toward a "balance of forces" with the U.S. through the development of nuclear weapons.

Another South Korean government official said, "It seems like North Korea publicly used the expression 'balance of forces.'"

It apparently shows that Pyongyang has no will for talks aimed at dismantling its nuclear weapons program. (Yonhap)