North Korea on Monday stepped up criticism of a massive joint military exercise involving tens of thousands of US and South Korean troops.
US and South Korean authorities have defended the six-day "Key Resolve" manoeuvres, which began on Sunday, as a defensive-oriented exercise to test military readiness.
The North's state-run Korean Central Broadcasting Station called the wargames a "frantic" move.
"An extremely dangerous situation is prevailing on the Korean peninsula due to the frantic war moves by the US imperialists and South Korean forces," it said in a report monitored by Yonhap news agency.
The North's military and people are ready to strike back in case of any attack, it said.
There are currently about 28,000 US troops backing up South Korea's forces against any threat from the North's 1.1 million-strong military.
An unspecified number of South Korean soldiers and about 27,000 US troops including 15,000 from the US mainland took part in the exercise.
It also involved the US aircraft carrier Nimitz, two US Aegis-equipped destroyers, a nuclear-powered submarine and US armoured combat vehicles.
The exercise comes as international efforts to dismantle North Korea's nuclear weapons programmes have reached stalemate.
On Sunday, a North Korean army spokesman denounced the exercises as "an open and blatant challenge" to the disarmament negotiations.
US overtures at six-party negotiations were "nothing but a crafty charade intended to cover up its preparations for a nuclear war" against North Korea, he said.
North Korea, which staged its first nuclear test in 2006, returned to six-party talks grouping the two Koreas, the United States, China, Russia and Japan.
But a disarmament deal in February last year has been held up since the North missed a year-end deadline to disable nuclear facilities and declare all relevant programmes.
Key Resolve aims to test the South's ability to host more than 600,000 US troops who would be deployed in the case of war.
The drill is the first conducted under a scenario where South Korea has regained wartime control of its troops from the United States.
South Korea ceded operational control over its own troops to the US-led United Nations Command during the Korean War. It regained peacetime control over its military in 1994 and is due to regain wartime command by April 2012.
