SEOUL, South Korea -- The United States and Japan agreed Friday to strengthen cooperation on missile defense amid concerns of a possible long-range rocket launch by North Korea.
The accord came as U.S. forces ended five days of Pacific war games -- the largest in the region since the Vietnam War. The exercise brought together three aircraft carriers along with 22,000 troops and 280 warplanes off the island of Guam.
In Tokyo, Japanese Foreign Minister Taro Aso and U.S. Ambassador Thomas Schieffer signed documents about cooperation on ballistic missile defense development. Japan's Defense Agency also said a high-resolution radar that can detect a ballistic missile has been deployed at a base in northern Japan.
North Korea has made recent moves that would enable it to launch a long-range missile, U.S. and Asian officials have said. Intelligence reports say fuel tanks have been seen around a missile at North Korea's launch site on its northeastern coast, but officials say it's difficult to determine if the rocket is actually being fueled by looking at satellite photos.
The North has said it is willing to talk with Washington about its missile concerns, repeating its long-held desire for direct meetings with the Americans. Washington has refused, and insists it will meet the North only in six-nation talks aimed at ridding Pyongyang of its nuclear weapons program.
South Korean Unification Minister Lee Jong-seok said Friday that "it seems clear that even if North Korea fires a missile, the United States would not make a compromise."
Lee said a "series of activities by North Korea" were consistent with a missile launch and pressed the North to return to six-nation talks on its nuclear program.
"North Korea should immediately halt moves of its missile launch," Lee said.
South Korean Foreign Minister Ban Ki-moon is seeking to visit China next week to discuss the missile issue, but plans have not been confirmed.
U.S. officials have warned North Korea that a missile launch could have serious repercussions.
"We still hope that they recognize that launching that missile would only isolate them further, and that they will make the right decision and not launch the missile," U.S. Ambassador to South Korea Alexander Vershbow told The Associated Press on Friday in Seoul.
He spoke after a ceremony marking the anniversary of the 1950 start of the Korean War, which ended in a 1953 cease-fire that has yet to be replaced by a peace treaty.
The U.S. military said Thursday it had successfully tested a missile defense system against a medium-range missile in a previously scheduled exercise.
However, U.S. National Security Adviser Stephen Hadley said this week the U.S. missile defense system had "limited operational capability" to protect against weapons such as the long-range missile the North is possibly moving to launch.