TOKYO It's easy to write off North Korea's threats to strike the United States with a nuclear-tipped missile as bluster: it has never demonstrated the capability to deploy a missile that could reach the Pacific island of Guam, let alone the mainland U.S.
But what about Japan?
Though it remains a highly unlikely scenario, Japanese officials have long feared that if North Korea ever decides to play its nuclear card it has not only the means but several potential motives for launching an attack on Tokyo or major U.S. military installations on Japan's main island. And while a conventional missile attack is far more likely, Tokyo is taking North Korea's nuclear rhetoric seriously.
On Monday, amid reports North Korea is preparing a missile launch or another nuclear test, Japanese officials said they have stepped up measures to ensure the nation's safety. Japanese media reported over the weekend that the defense minister has put destroyers with missile interception systems on alert to shoot down any missile or missile debris that appears to be headed for Japanese territory.
"We are doing all we can to protect the safety of our nation," said chief Cabinet spokesman Yoshihide Suga, though he and Ministry of Defense officials refused to confirm the reports about the naval alert, saying they do not want to "show their cards" to North Korea.
Sen. John McCain, R-Ariz., said Sunday on "Face the Nation" that news that North Korea is expected to go ahead with a missile launch signals "a catastrophe of enormous proportions."
McCain said what happens next will depend largely on China, whose relationship with North Korea, a senior official tells CBS News, is at a historic low.
"China can cut off their economy if they want to," McCain said. "Chinese behavior has been very disappointing, whether it be on cyber security, whether it be on confrontation on the South China Sea, or whether it be their failure to rein in what could be a catastrophic situation."
North Korea, meanwhile, issued a new threat against Japan.
"We once again warn Japan against blindly toeing the U.S. policy," said an editorial Monday in the Rodong Sinmun, the official newspaper of its ruling party. "It will have to pay a dear price for its imprudent behavior."
Following North Korea's third nuclear test in February, Japanese experts have increasingly voiced concerns that North Korea may already be able to hit - or at least target - U.S. bases and major population centers with nuclear warheads loaded onto its medium-range Rodong missiles.
"The threat level has jumped" following the nuclear test, said Narushige Michishita, a former Ministry of Defense official and director of the Security and International Studies Program at Tokyo's National Graduate Institute for Policy Studies.