South Korean experts said Sunday they wouldn't rule out the possibility of a second, secret plutonium plant in North Korea, though it would be tricky for North Korea to build such a facility.
"It is possible that there is a second plant for producing plutonium in North Korea if the North Korean claims that they finished reprocessing spent nuclear fuel rods are true," said Cheon Seong-whun, a South Korean arms control expert.
Another South Korean analyst of North Korean affairs, Koh Yu-hwan, said it would be hard for North Korea to run a second, secret plant because U.S. spy satellites might detect it. The reprocessing plant at Yongbyon, which analysts believe has not been running at full capacity, is easily visible in satellite photographs.
But North Korea, which was devastated by U.S. air power during the 1950-53 Korean War, has untold numbers of underground military sites. In 1999, North Korea allowed U.S. nuclear inspectors to visit a suspicious underground site in exchange for a huge food shipment. The search turned up nothing. Critics called it a case of blackmail.
If the suspicions are true that a second covert plant has begun producing weapons-grade plutonium (search) in North Korea — as a Saturday New York York Times report alleged — then diplomatic efforts to resolve the nuclear crisis and dismantle Pyongyang's weapons facilities could well be rattled.
The concerns also pose a dilemma for President Bush if diplomacy fails and he is forced to consider military action.
Visiting Seoul, British Prime Minister Tony Blair said Sunday that North Korea must not be allowed to develop nuclear weapons, and that multilateral talks involving the United States, China, Japan and the two Koreas were essential to a resolution.
"This is a situation which I think has to be handled with a special sensitivity," Blair said at a joint news conference with South Korean President Roh Moo-hyun.
"We cannot have a situation in which North Korea not only continues to develop a nuclear weapons program, but proliferates and exports that technology around the world."
Blair, who flew to Beijing later Sunday, was expected to discuss the issue with Chinese officials Monday.
Roh and Blair agreed Sunday on the need for dialogue to resolve the crisis.
"We want to resolve the issue of North Korea and its nuclear weapons program and the export of nuclear technology by peaceful and constructive dialogue," Blair said.
Roh, for his part, downplayed the allegations pointing to a second nuclear plant and the White House wouldn't confirm the Times' assertion that there is strong new evidence for the facility's existence.
"When we compare the current situation with six months ago, I think some of the dangers have subsided" on the Korean Peninsula (search), Roh said. He praised Washington for putting pressure on North Korea on the issue while maintaining a "friendly attitude."
A senior State Department official, speaking in Washington on condition of anonymity, said there was no hard evidence to back up the idea that there is a secret plutonium processing plant.
"There are suspicions such exists, but no hard evidence," the official said.
White House Press Secretary Scott McClellan (search) said he couldn't discuss intelligence matters and thus couldn't confirm the report.
McClellan did say that North Korea has already publicly acknowledged it is producing nuclear weapons and has "taken a number of escalating steps in recent months," including the expulsion of international weapons inspectors from its borders and the restarting of nuclear facilities.
"Reprocessing to recover plutonium (search) is a clear indication that North Korea is seeking to enlarge its nuclear arsenal despite repeated calls from the international community to reverse the provocative steps it has taken in its nuclear weapons program," said McClellan.
"We will continue working closely with our friends and allies toward a complete, verifiable and irreversible end to North Korea's nuclear weapons program."
Former Justice Department prosecutor John Loftus said Sunday on the Fox News Channel that U.S. satellites scanning North Korea have detected enriched uranium and craters for carrying small nuclear weapons. He said the missiles have the range to hit Hawaii "if they could find it," but that the current system for directing such weapons to a specific target is not accurate.
Loftus said it's only a matter of time before the North Koreans perfect the system, however.
"This is an alarming development," he said of the possible second plant.
The nuclear weapons crisis flared last October when U.S. officials said North Korea admitted having a secret nuclear program in violation of a 1994 pact with the United States. Then President Bill Clinton had been considering military strikes against the country in 1994 to thwart further development of nuclear weapons, according to Loftus and the Times.
More recently, North Korea has said it has reprocessed its spent nuclear fuel rods, a key step toward the production of nuclear weapons.
Now U.S. and U.N. officials have begun watching for signs that North Korean capital city Pyongyang has begun producing plutonium, a process that emits a kind of krypton gas that U.S. sensors can detect.
The Times reported Sunday that American officials confirmed sensors on the North Korean border have detected elevated levels of krypton 85.
But the gas is apparently not emanating from North Korea's known Yongbyon nuclear site, leading American and Asian officials to believe North Korea has secretly built a second plant for producing plutonium, according to the Times.
International Atomic Energy Agency spokeswoman Melissa Fleming said Sunday the agency (which sent the now-expelled inspectors into North Korea) does not test gases on the country's border, so would not be able to confirm whether gases emitted during plutonium conversion are unusually high — even if IAEA inspectors were in the country.
The U.S. Embassy in Seoul declined to comment. A South Korea official said there had been no official discussion between Seoul and Washington on any secret facility, according to Yonhap, a South Korean news agency.
This month, North Korea told U.S. officials that it had reprocessed all of its 8,000 spent nuclear fuel rods, a procedure that experts say could yield enough plutonium to make several nuclear bombs within months. U.S. officials are not sure whether North Korea is telling the truth or bluffing in order to win concessions in any negotiations.
Japanese Prime Minister Junichiro Koizumi's spokesman, Yu Kameoka, said he had no information on the possibility of a second North Korean site. Japan, which is within range of North Korean missiles, coordinates with the United States on defense issues.
A Chinese envoy visited North Korea and the United States in the past week in an effort to bring the two adversaries together. North Korea wants one-on-one talks with Washington, but U.S. officials prefer a multilateral format.
The Associated Press contributed to this report.