ROUGH CUT (NO REPORTER NARRATION)

STORY: South Korean and U.S. Air Forces teamed up on Wednesday for combined military exercise in an annual national defense drill.

A total 62 aircraft, including F-16 and F14k fighters, as well as an early warning aircraft "Peace Eye" were mobilized for the drill called "Max Thunder".

"In 2015, there will be a transition of operation control from U.S. forces to the Republic of Korea. But our objective remains same that is to deter, defend, and if necessarily, defeat any aggression against South Korea," said Lieutenant General Jan-Marc Jouas of U.S. Air Force.

The combined air force exercise was part of the annual 'Hokuk' exercise, which has been conducted since 1996.

The U.S. team pledged to retain its strong military alliance with the South.

Recently, Pyongyang threatened to attack if South Korean activists send more propaganda leaflets across the border into the North.

Defectors and anti-North Korea activists have frequently launched balloons carrying propaganda and cash across the border.

The warning of a "merciless military strike" was the most explicit in months and the first since Kim Jong-un, believed to be 28 years old, took power in December 2011.

South Korea had said it would retaliate against any North Korean attack, raising tensions on the border which separates two countries that remain technically at war because the 1950-53 Korean war ended with only an armistice.

North Korea shelled a South Korean island in November 2010, killing civilians and prompting counter-fire from the South.