Seeking a world free of atomic arms, president Barack Obama today asserted that the US and others will not "be cowed" by North Korea's threats to step up its nuclear programme, and will advance the goal of securing all of the world's "vulnerable" material within four years.

"Next year at our Nuclear Security Summit, we will advance our goal of securing all of the world's vulnerable nuclear materials within four years," he said in his major policy speech on Asia at the Suntory Hall here before a 1,500-strong audience.

Obama also stressed on the need of a world free of nuclear weapons for achieving "common security".

Noting that strengthening the global non-proliferation regime is not about singling out individual nations, he said it is about all nations living up to their responsibilities.

"That includes the Islamic Republic of Iran. And it includes North Korea," he said. "For decades, North Korea has chosen a path of confrontation and provocation, including the pursuit of nuclear weapons."

"It should be clear where that path leads. We have tightened sanctions on Pyongyang. We have passed the most sweeping UN Security Council resolution to date to restrict their weapons of mass destruction activities," he said.

"We will not be cowed by threats, and we will continue to send a clear message through our actions, and not just our words: North Korea's refusal to meet its international obligations will lead only to less security, not more," Obama said.

Obama also said that the United States is prepared to offer North Korea a different future. "Instead of an isolation that has compounded the horrific repression of its own people, North Korea could have a future of international integration.

"Instead of gripping poverty, it could have a future of economic opportunity where trade, investment and tourism can offer the North Korean people the chance at a better life.

And instead of increasing insecurity, it could have a future of greater security and respect," he said.

Obama said the path for North Korea to realise this future is clear: a return to the six-party talks on its nuclear issue; upholding previous commitments, including a return to the Nuclear Non-Proliferation Treaty; and the full and verifiable denuclearisation of the Korean peninsula.

"No two nations on earth know better what these (nuclear) weapons can do, and together we must seek a future without them.

This is fundamental to our common security, and this is a great test of our common humanity. Our very future hangs in the balance," Obama said.

"Let me be clear: so long as these weapons exist, the United States will maintain a strong and effective nuclear deterrent that guarantees the defence of our allies including South Korea and Japan," he said.

However, he warned that an escalating nuclear arms race in this region would undermine decades of growing security and prosperity.