TOKYO - U.S. Secretary of State Hillary Clinton used her first overseas trip to declare a new era in relations with Asia, seeking a more global framework of co-operation on common threats like financial instability, nuclear proliferation and climate change.

But the protracted issue of reining in North Korea's nuclear ambitions cast a long shadow as Clinton opened a weeklong tour of Japan, Indonesia, South Korea and China in Tokyo.

"I have come to Asia on my first trip as secretary of state to convey that America's relationships across the Pacific are indispensable to addressing the challenges and seizing the opportunities of the 21st century," she said.

"We will be looking for ways to collaborate on issues that go beyond just our mutual concerns to really addressing global concerns," Clinton said at a ceremony to commemorate the arrival of the first secretary of state ever to make Japan her first overseas stop.

Yet Clinton's message was in danger of being overshadowed by a surge in bellicose rhetoric from North Korea, which just hours before vowed to press ahead with test-firing what wary neighbouring governments, particularly Japan and South Korea, believe is a long-range missile.

Japan, with an unpopular government and struggling with deep economic woes, is particularly jittery at the moment and Clinton aims to reassure the country of its importance in the international arena.

"The bilateral relationship between the United States and Japan is a cornerstone in our efforts around the world," she said. On Tuesday, she is expected to announce that she will send a special U.S. envoy to a Japanese-hosted donors conference for Pakistan.

In addition to meeting with top government officials and members of the opposition, Clinton will sign an agreement to move about 8,000 of the 50,000 marines on the island of Okinawa to the U.S. Pacific territory of Guam.

But, North Korea looms large over her visit. She has promised to meet with the families of Japanese citizens kidnapped by North Korea in the 1970s and 1980s. "We do want to press the North Koreans to be more forthcoming with information," she said en route to Tokyo.

Last week, she had warned North Korea against any "provocative action and unhelpful rhetoric" amid signs the Stalinist country was preparing to test fire a missile capable of reaching the western United States.

But on Monday, the 67th birthday of North Korean leader Kim Jong Il, Pyongyang claimed it has the right to "space development" - a term it has used in the past to disguise a missile test as a satellite launch. When North Korea test-fired a long-range missile in 1998, it claimed to have put a satellite into orbit.

On Sunday, Clinton said told reporters aboard her plane that North Korea needs to live up to commitments to dismantle its nuclear programs, saying Washington is willing to normalize ties with it in return for nuclear disarmament.

"The North Koreans have already agreed to dismantling," she said. "We expect them to fulfil the obligations that they entered into."