Tuesday, June 20, 2006; Posted: 12:42 p.m. EDT (16:42 GMT)

HAGATNA, Guam (AP) -- Three aircraft carriers filled the skies with fighters as one of the largest U.S. military exercises in decades got underway Tuesday off this island in the western Pacific.

For the first time ever, a Chinese delegation was sent to observe the U.S. war games. But as the show of American military power began, North Korea -- one of the region's most unpredictable countries -- was rattling some swords of its own.

The maneuvers, dubbed "Valiant Shield," bring three carriers together in the Pacific for the first time since the Vietnam War. Some 30 ships, 280 aircraft and 22,000 troops will be participating in the five-day war games, which end Friday.

The exercises are intended to boost the ability of the Navy, Air Force and Marines to work together and respond quickly to potential contingencies in this part of the world, U.S. military officials said. Even U.S. Coast Guard vessels were joining in the maneuvers.

"The exercises are taking place on land, sea, air, space and cyberspace," said Senior Master Sgt. Charles Ramey. "They cover the whole spectrum."

The maneuvers mark the first major operation in this remote U.S. territory about halfway between Hawaii and Japan since the announcement last month that 8,000 Marines would be moved here from Okinawa in part of the biggest realignment of the U.S. forces in Asia in decades.