A US frontline division has mobilized about 6,000 troops for its annual "Iron Artep" exercise, which began last weekend near the border with North Korea, a US military official said.

"The exercise, contucted annually by the 2nd Infantry Division to test combat readiness, will run through March 5," he said.

The US military newspaper Stars and Stripes said the exercise included obstacle-breaching attacks, a bridging drill and relief-in-place training.

It comes at a sensitive period with North Korea engaged in six-party talks in Beijing to resolve the standoff on its nuclear programs.

The division is the backbone of 37,000 US troops stationed in South Korea under a mutual defense pact dating back to the 1950-53 Korean War to deter North Korea's 1.1 million strong army.

WAR.WIRE