By Phil Stewart
SEOUL (Reuters) - U.S. Defense Secretary Leon Panetta branded North Korea a "serious threat" on Wednesday, as the U.S. military cast a cautious eye on diplomatic engagement with Pyongyang that it fears could be short-lived.
The United States and North Korea appear to be inching toward a resumption of six-party talks aiming to wean the North of its nuclear programs. Envoys from Pyongyang and Washington met in Geneva this week.
The United States and North Korea also reached an agreement this month on resuming recovery of the remains of American soldiers killed in the 1950-53 Korean War, activities halted since 2005.
But Panetta, even as he welcomes those steps, has used harsh words to describe North Korea during his first trip to Asia since taking over the Pentagon in July.
He described Pyongyang as "reckless" on Monday and wrote that the North remained "a serious threat" in an op-ed published in a South Korean newspaper ahead of his arrival in Seoul on Wednesday.
"I come here because in many ways this is the front line," Panetta said, addressing several hundred U.S. and South Korean forces in Seoul.
A senior U.S. defense official, briefing reporters traveling with Panetta, said that it was important that military preparations be "aligned with where things are in the diplomatic process" given the cyclical nature of ties.
"Our experience unfortunately has been that our North Korean friends go through cycles of diplomatic engagement and provocation and we need to be prepared for how that cycle may play itself out on the next turn," the official said.
Should Pyongyang again find engagement has run its course, analysts fear it could test another nuclear weapon or pick new fights with Seoul. North Korea was blamed for killing some 50 South Koreans in two attacks near their contested maritime border in 2010.
The North also unveiled a uranium enrichment facility last year that gives it a second route to making an atomic bomb.
North Korea's Kim Jong-il is gradually preparing to be replaced by his son Kim Jong-un, and some experts warn that the succession of power could trigger provocations. That is a concern shared by Panetta.
"I think we always have to be prepared, from a security point of view, to deal with the likelihood that as succession develops in North Korea that it could lead to greater provocations," he told reporters on Friday.
South Korea is Panetta's last stop on a week-long trip that has included visits to Japan and Indonesia. At every opportunity, Panetta has been reassuring allies in the region that the U.S. military will maintain a strong posture in the Pacific despite looming defense spending cuts at home.
This is particularly important in places like South Korea and Japan, where the United States has about 80,000 forces deployed and where U.S. allies are nervously watching China's military buildup and increasing assertiveness in the South China Sea.
Panetta said the U.S. withdrawal from Iraq this year and the gradual drawdown in Afghanistan would allow the United States to shift more attention to Asia.
"All of the success we've had now gives us the opportunity to make sure we make the kind of investment we need to make in the Pacific," Panetta said earlier in the day in Japan.
Addressing U.S. troops in Japan on the flight deck of the Navy command ship USS Blue Ridge, Panetta said the Asia-Pacific region was important to the United States.
"This is an important area. There are continuing threats that we have to address ... threats of rising powers, threats from North Korea, with nuclear proliferation, threats from cyber," he said, Tokyo Bay behind him in the distance.
"We've got a lot of threats that continue to face this country."
(Editing by Sugita Katyal)