Air bases in Aurora and Colorado Springs, Colo. are on heightened alert but no one would say why.
The Cheyenne Mountain Air Station and Buckley Air Force Base were among four bases nationwide that went on higher alert.
Vandenberg Air Force in California and Patrick Air Force Base in Florida were also on heightened alert, after the U.S. Space Command in Colorado Springs issued the security increase.
North American Aerospace Defense Command, headquartered deep inside Cheyenne Mountain in Colorado Springs, went to “Bravo-Plus” alert status as part of the heightened alert.
There are five levels of alert used by NORAD are: normal, Alpha (low), Bravo (medium), Charlie (high) and Delta (critical). “Bravo-Plus” is slightly higher than a medium threat level.
Space Command would not comment on the reason for the security increase but reports indicated that it might be connected with a possible North Korean missile test directed toward the United States.
On Monday, North Korea said it would respond to a pre-emptive U.S. military attack with an “annihilating strike and a nuclear war,” the state-run media reported. On Friday, Pyongyang accused the United States of driving the situation on the Korean Peninsula “to the brink of war,” and said it is fully prepared to counter any U.S. aggression. That is about the time the increased security alert was issued.
The North Korean threat of retaliation, which is often voiced by its state-controlled media, comes amid U.S. official reports that Pyongyang has shown signs of preparing for a test of a long-range missile. North Korea claims it has the right to such a launch.
Monday’s report accused Washington of escalating military pressure on the country with war exercises, a massive arms buildup and aerial espionage by basing new spy planes in South Korea.
“This is a grave military provocation and blackmail to the DPRK, being an indication that the U.S. is rapidly pushing ahead in various fields with the extremely dangerous war moves,” the dispatch said.
“The army and people of the DPRK are now in full preparedness to answer a pre-emptive attack with a relentless annihilating strike and a nuclear war with a mighty nuclear deterrent,” the report said.
DPRK stands for the North’s official name, the Democratic People’s Republic of Korea.
North Korea routinely accuses the U.S. of aerial espionage, issuing a tally of such flights at the end of every month. The U.S. military doesn’t comment, although it acknowledges monitoring North Korean military activity.
Washington and Japan have said in recent weeks that spy satellite images show North Korea has taken steps to prepare a long-range Taepodong-2 missile for a test-launch.
Estimates for the range of the missile vary widely, but at least one U.S. study said it could be able to reach parts of the United States with a light payload.
Speculation that Pyongyang could fire the missile has waned in recent days since the country’s top ally and a major source of its energy supplies, China, reportedly urged North Korea not to go ahead with the test.
A news report said Monday that China has offered a new proposal over the stalled six-party talks on North Korea’s nuclear program.
Chinese State Councilor Tang Jiaxuan told Ichiro Ozawa, the head of Japan’s main opposition party, that China had relayed the proposal to Japan, the two Koreas, the United States and Russia, Kyodo News agency reported, citing party officials.
The report did not elaborate on the proposal. An opposition party spokesman in Tokyo could not be reached for comment.
Ozawa is in Beijing for a six-day stay that party officials hope will include a meeting with Chinese President Hu Jintao, according to Kyodo.
Meanwhile, a South Korean government official said Seoul is considering buying U.S. shipborne SM-2 missiles to bolster its missile-defense system.
The move is the latest by South Korea and Japan to strengthen their defenses amid signs of the North Korean missile test. Seoul announced last week the purchase of Patriot interceptor missiles from Germany.
SM-2 missiles, however, are reportedly effective against cruise missiles and at striking aircraft but would not be able to hit a long-range missile.
“I understand that we have requested information” on the missiles for purchase, said Park Sung-soo, an official at the Defense Acquisition Program Administration, without elaborating.
The U.S. Defense Security Cooperation Agency notified Congress of the possible sale last week, according to its Web site. The order would be for 48 SM-2 Block IIIB tactical standard missiles and associated equipment and training.
The agency estimated the cost at $111 million.
South Korea would use the missiles to defend its new KDX-III AEGIS destroyer, and already uses SM-2 Block IIIA missiles in its ship combat systems, the agency said. The prime contractor will be Raytheon Systems Company of Tucson, Ariz., the agency said.
In early June, the Pentagon notified Congress that the U.S. could sell Japan nine upgraded SM-3 missiles and related equipment for use on their AEGIS destroyers. The price tag was put at up to $438 million.
Japan already has four AEGIS destroyers operating with SM-2 missiles, and two more are under construction, the Pentagon said.
Last week, officials said that South Korea had notified Germany of its interest in buying Patriot interceptor missiles, with the aim of replacing its outdated Nike-Hercules missiles by 2010.
The Nike-Hercules missiles have served as South Korea’s main anti-aircraft weapons for some 40 years, but the Patriot missiles are more advanced at intercepting and destroying incoming ballistic missiles, cruise missiles and enemy aircraft.
South Korea’s military as yet has no Patriots, although some are already deployed on U.S. bases in the country, where about 29,500 U.S. troops are stationed as a deterrent against communist North Korea.