SEOUL, South Korea (Reuters) -- The United States has moved its ground-based interceptor missile defense system from test mode to operational amid concerns over an expected North Korean missile launch, a U.S. defense official said Tuesday.
South Korean Foreign Minister Ban Ki-moon said on Tuesday that North Korea had put its long-range Taepodong-2 missile on a launching pad, but it was unclear if the missile was fully fueled.
Meanwhile, Pyongyang said it would not be bound by a 2002 treaty prohibiting launches of ballistic missiles.
The U.S. defense official, speaking on condition of anonymity, confirmed a Washington Times report that the Pentagon has activated its missile defense system, which has been in the developmental stage for years.
"It's good to be ready," the official said.
U.S. officials say evidence such as satellite pictures suggests Pyongyang may have finished fueling the Taepodong-2 missile, which some experts said could reach as far as Alaska. (Watch what satellite images reveal -- 1:58
"There's real caution in how to characterize it so as to not be provocative in our own approach," the defense official said of the move to activate the system.
The Pentagon and U.S. State Department have said a North Korean missile launch would be seen as "provocative."
While military officials note the United States has a limited missile defense system, they have so far declined to comment on any details about the capabilities or potential use of the system to intercept a North Korean missile.
Meanwhile, South Korea's Ban called on Pyongyang to scrap test plans while saying the missile was on the pad.
"It is not sure that they have put the fuel in the rockets, but it seems to be sure that they have assembled these missiles in the launching pad," Ban told reporters in Geneva, Switzerland.
According to Japan's Kyodo news agency, North Korea's Foreign Ministry said Tuesday any long-range missile test will not be bound by the Pyongyang Declaration. (Watch how Japan plans to respond to a test launch -- 1:11
Under that 2002 agreement with Japan, North Korea pledged to uphold all international treaties on nuclear issues, extend a moratorium on ballistic missile launches and resolve issues related to the "lives and security" of Japanese nationals.
Meanwhile, China, the North's closest ally, said it had no details of any test-flight preparations and called for calm.
South Korea's weather agency forecast overcast skies and storms on Tuesday in North Hamgyong province, where North Korea has a launch site, and said this should be the pattern for the rest of the week as a storm front moves through.
Analysts say clouds and storms would make it difficult for North Korea to track a missile once in flight, decreasing the likelihood of a launch.
"You don't want to test launch a missile into a storm," said Peter Beck, a Korea analyst in Seoul for the International Crisis Group.
Reports of test preparations coincide with a stalemate in six-party talks on unwinding Pyongyang's nuclear arms programs.
Some analysts believe that North Korea is piqued world attention has shifted to concerns about Iran's nuclear ambitions and angered at a U.S. crackdown that has frozen hard currency income from alleged illegal activities such as money laundering.
Beck said that by raising the prospect of a missile test, the Stalinist state had successfully grabbed global attention and rattled security concerns, but he was not sure if Pyongyang would scrap the launch in the face of pressure or go ahead.
"If they are really playing a finesse game they will back away but ... they are not known for their finesse game," he said.
Alexander Vershbow, U.S. ambassador to Seoul, said Tuesday any work on a potential delivery system, such as a missile, for a nuclear weapon creates a serious security threat.
Proliferation experts have said it is not likely North Korea has the technology to miniaturize a nuclear weapon so that it can be mounted on a missile.
North Korea shocked the world in 1998 when it fired a missile, part of which flew over Japan and landed in the Pacific Ocean. Pyongyang trumpeted that as a satellite launch.
"A missile launch is North Korea's second-biggest 'card' after a nuclear test, and they would have to seriously consider the timing," said Masao Okonogi, a Korea expert at Keio University in Tokyo.
"I think this is a bluff," he said.