The Republic of Korea (ROK) and the United States launched on Tuesday an annual joint military exercise aimed at enhancing their interoperability in defense.

The 10-day computer-assisted command post exercise, dubbed Ulchi Freedom Guardian, brought together some 530,000 ROK and US troops on the Korean Peninsula and at US military headquarters in the Pacific and the US, according to the Combined Forces Command (CFC) here.

The US-led United Nations Command has informed the Democratic People's Republic of Korea (DPRK) of the defensive nature of the routine drill, according to the CFC.

The drill is "focused on preparing, preventing and prevailing against the full range of current and future external threats" to the ROK and the region, said General James D. Thurman, Combined Forces Command commander.

"We are applying lessons learned out of Iraq and Afghanistan, as well as those garnered by the alliance's recent experiences with the DPRK provocations on the peninsula and past exercises," he added.

The DPRK's official newspaper Rodong Sinmun on Tuesday said the muscle-flexing is provocative and warned about an "all-out war", adding that "the Korean Peninsula is faced with the worst crisis ever".

The DPRK recently said it is ready to return to the long-stalled Six-Party Talks with no preconditions attached and would implement the Sept 19 joint statement on the principle of simultaneous action.

However, the no-preconditions stance was lukewarmly received by both the US and the ROK.

Pyongyang's pledge was the latest of its efforts to revive the Six-Party Talks. Similar moves in the past have produced no substantial results and have always been interrupted from time to time due to a series of incidents, including the sinking of an ROK naval vessel last March and fighting between the DPRK and the ROK in waters off the west coast of the peninsula in November.

A lack of trust and a wait-and-see attitude taken by the US and the ROK have also complicated the peninsula's nuclear conundrum.

China has consistently urged all parties to exercise maximum restraint and to do nothing that would put regional peace and stability in jeopardy. China is not in favor of setting pre-conditions for the talks.

China has urged the US and the ROK not to trigger another round of tension in the region during their war games and to fully consider the security concerns of neighboring countries.