(Adds Moon meeting with Austin)
By Phil Stewart and Hyonhee Shin
SEOUL, Dec 2 (Reuters) - The defence chiefs of the United States and South Korea said on Thursday they would review and update ways to deter North Korea, even as they emphasised a growing regional role for Seoul.
North Korea's missile and weapons developments are increasingly destabilising for regional security, U.S. Defence Secretary Lloyd Austin said after talks with his South Korean counterpart, Suh Wook, but the two sides also discussed issues beyond the Korean peninsula.
For the first time, their joint statement affirmed "the importance of preserving peace and stability in the Taiwan Strait."
It mirrored language used for the first time by South Korean President Moon Jae-in in May when he met with U.S. President Joe Biden in Washington. It's a sensitive issue for South Korea, which has tried to balance its economic relationship with China with Washington's push for allies to counter Beijing's growing power.
The statement came the same day that South Korea's national security adviser travelled to China to meet its top diplomat. It also followed remarks on Wednesday by Japan's former prime minister, Shinzo Abe, suggesting that a Chinese invasion of Taiwan would be a danger for Japan.
Austin and senior U.S. military commanders were in Seoul for the first such annual military talks with South Korean officials since Biden took office in January, and the last before Moon leaves office in May.
North Korea has continued to rebuff U.S. entreaties for diplomacy since Biden took over from Donald Trump, who had three summits with leader Kim Jong Un.
The United States calls on the North to engage in dialogue, Austin told a news conference, saying diplomacy is the best approach to pursue with North Korea, backed up by a credible deterrent.
This week the Pentagon released a global posture review that calls for additional cooperation with allies and partners to deter "potential Chinese military aggression and threats from North Korea," including a previously announced decision to permanently base an attack helicopter squadron and artillery division headquarters in South Korea.
The United States stations about 28,500 troops in South Korea as a legacy of the 1950-1953 Korean War, which ended in an armistice but not a peace treaty.
In a meeting with Austin on Thursday evening, Moon asked that the United States support his push for an "end of war declaration" aimed at reducing tensions with North Korea and jump-starting talks, said a spokesperson for South Korea's presidential Blue House.
Austin responded by paying tribute to Moon's efforts to improve relations with North Korea, the spokesperson said in a statement.
CHANGING SECURITY ENVIRONMENT
A changing security environment prompted the United States and South Korea to agree to update strategic guidance about how they plan for a potential conflict with North Korea, as well as review their combined military command, Suh said.
"The Strategic Planning Guidance from 2010 still remains effective, but we've shared the need for a new war plan that could reflect evolving threats from North Korea and changes from our own defence reform and a combined command structure, as well as overall strategic environment," he said at the news conference.
U.S. and South Korean officials cautioned that the updates to the war plans are routine and not a preparation for war.
Currently, the United States would command allied troops in the event of war, but South Korea has been seeking to gain "operational control" (OPCON).
Moon's goal of OPCON transfer by the time he leaves office could not be achieved, as a scheduled joint review was not conducted amid the COVID-19 pandemic.
Suh said the two sides made progress on meeting conditions for OPCON transfer to South Korea and agreed to assess the future command's full operational capability next year.
The United States reaffirmed its commitment to providing extended deterrence to South Korea, including using its nuclear weapons, along with convention and missile defence capabilities.
But America's approach to nuclear deterrence could change. Biden is carrying out a review of U.S. nuclear weapons policy, with hopes for a more tailored role for nuclear arms, experts say.
It's unclear whether Biden might break precedent by declaring a "no first use" policy, a move that critics say would weaken U.S. deterrence. (Reporting by Hyonhee Shin and Phil Stewart; Writing by Jack Kim and Josh Smith; Editing by Stephen Coates, Gerry Doyle and Emelia Sithole-Matarise)