WASHINGTON -- The Air Force prepared Wednesday to resume reconnaissance flights off the coast of North Korea, 10 days after Korean fighter jets intercepted an Air Force plane equipped to monitor missile tests, a senior U.S. official said.

It was not immediately clear whether the Air Force planned to use fighter jets to escort the reconnaissance flights, but officials said earlier this week that escorting was unlikely. The United States has always asserted its right to conduct aerial surveillance in international airspace without armed escort, and rarely has encountered hostile interference.

On March 2, four armed North Korean fighter jets intercepted an RC-135S Cobra Ball over the Sea of Japan about 150 miles off North Korea's coast. U.S. officials said one of the fighters used its radar in a manner that indicated it might be preparing to attack, although no shots were fired.

The U.S. plane broke off its mission and returned unharmed to its base at Kadena, Japan. Since then there have been no U.S. reconnaissance flights off North Korea's coast, officials said.

The official who, speaking on condition of anonymity, said the Air Force was preparing to resume reconnaissance flights provided no other details.

Navy Lt. Cmdr. Jeff Davis, a Pentagon spokesman, said he could not comment.

"As we have stated, we continue to fly legal reconnaissance missions in a variety of places around the world, but we cannot comment on specific plans," Davis said.

Davis said the North Korean pilots in the March 2 intercept appeared to be trying to draw the RC-135S to North Korea.

"Clearly the actions of the North Korean air crews, including hand gestures by one of the pilots, suggests that this was a coordinated attempt to force our aircraft to divert to North Korea," Davis said.

First since 1969

The Pentagon said the March 2 intercept was the first such incident with North Korea since April 1969, when a North Korean plane shot down a U.S. Navy EC-121 surveillance plane, killing all 31 Americans aboard.

The United States uses a variety of intelligence, surveillance and reconnaissance methods to monitor North Korea's military activity, including developments in its nuclear weapons program.

Tensions between the United States and communist North Korea are mounting on a variety of fronts.

In recent months, North Korea has expelled U.N. monitors, withdrawn from a key nuclear arms-control treaty and restarted a nuclear reactor that had been mothballed for years under U.N. seal.

The Pentagon recently dispatched a dozen B-52 bombers and a dozen B-1 bombers to the Pacific island of Guam, as a precautionary move designed to discourage North Korea from military action.

The U.S. Navy has announced plans to send the aircraft carrier USS Carl Vinson to South Korea to participate in a major U.S.-South Korean military exercise this month called Foal Eagle. The U.S. Air Force is sending six F-117 Nighthawk stealth fighters from their home base in New Mexico to South Korea to participate in the exercise.

North Korea's official Korean Central News Agency said Wednesday that the Bush administration was "watching for a chance to mount a pre-emptive attack on the nuclear facilities."

The Air Force RC-135S plane is equipped with multiple electronic receivers. It has large circular windows in the fuselage for the photography of foreign ballistic-missile tests at long range. The intelligence equipment aboard includes multiple infrared telescopes.

North Korea has conducted two missile tests in recent days and there is speculation that it may be preparing to test a longer-range missile.

The United States and North Korea have no formal diplomatic relations, and North Korea has said joint U.S.-South Korean military exercises are a prelude to a U.S.-led invasion.

The United States led a United Nations coalition of forces on behalf of South Korea against North Korea and Chinese forces in the 1950-53 Korean War. No peace treaty was ever signed.