North Korea yesterday accused the US of plotting a "nuclear attack" as US and South Korean soldiers staged a military exercise near the border with the communist country.
Pyongyang also slammed Washington's recent decision to send additional long-range bombers to Guam, about 3,200km from the Korean Peninsula.
North Korea claims that Washington is planning pre-emptive strikes on its military bases and nuclear facilities, which US officials believe are being used to make atomic bombs.
The North's state-run KCNA news agency said the US Department of Defense mapped out a strike plan including "not only cruise missile strikes and massive air raids, etc, but the use of tactical nuclear weapons."
North Korea's "army and people will take every possible self-defensive measure to cope with the US bellicose forces' new war moves," it said.
Tension over Pyongyang's suspected nuclear weapons development heightened last week after North Korean fighter jets briefly intercepted a US reconnaissance plane over the sea between the Korean Peninsula and Japan.
US officials also believe Pyongyang may be preparing to test fire another missile soon, following the launch of an anti-ship missile into the sea off its east coast late last month.
Pentagon is deploying 12 B-1 and 12 B-52 bombers to Guam to deter conflicts that could arise in the West Pacific.
"These moves indicate that the US Air Force is taking the lead in implementing the US imperialists' strategy to mount a pre-emptive attack on [North Korea]," said Pyongyang's official Rodong Sinmun newspaper.
During yesterday's joint exercise, hundreds of soldiers backed by tanks and armored vehicles crossed a river using a makeshift bridge. Two military helicopters hovered above.
The annual drill called Army Readiness Training Evaluation Program III involved some 7,000 troops and some 300 military vehicles. Washington keeps 37,000 troops in South Korea.
Washington says it wants to settle the dispute diplomatically, but has not ruled out a military option.
Meanwhile, US officials demanded that Pyongyang dismantle its nuclear facilities in Yongbyon during unofficial talks in Germany last month, a major Japanese daily said yesterday.
US diplomats also called for Pyongyang to allow International Atomic Energy Agency inspectors to return to verify that it wasn't enriching uranium for its purported nuclear weapons program during the meetings at the North Korean Embassy in Berlin on Feb. 20 to 21, the Asahi newspaper reported.
North Korea rejected the demands and the meetings ended in disagreement, the paper said, citing an unidentified former US official who attended the meeting.