WASHINGTON — Much of the United States' ground combat might is tied up in Iraq and Afghanistan, and the United States is reducing its infantry forces in South Korea.

But American air and sea power in east Asia, a key to almost any imaginable military conflict with North Korea, has grown in numbers and reach.

So the United States apparently has sufficient forces for the most likely military missions that would be required in a Korea crisis: perhaps a sea and air blockade, officials and analysts say.

But if North Korea attacks South Korea, the United States would face hard decisions about multiple wars. Soldiers and Marines getting ready to rotate into Iraq would have to be diverted to Korea, requiring the troops in Iraq to stay much longer.

Democratic Rep. Ike Skelton, a close observer of military issues, said in an interview yesterday that he worries a military crisis in North Korea would overstretch the Army and Marines.

Skelton said the Army has only two fully ready combat brigades available, one in Germany, the other in Kuwait. The rest are in Iraq or Afghanistan, are getting ready to deploy there, or have just returned.

The U.S. military has about 140,000 troops in Iraq and about 20,000 in Afghanistan.

One Army combat brigade is based in South Korea as part of a U.S. force numbering 28,000. That force has been pared down from 32,500 over the past few years and is scheduled to drop to 25,000 by 2008.

About 50,000 U.S. troops are in Japan; of those, about 8,000 Marines are scheduled to move from Okinawa to Guam.

Michael Green, senior adviser at the Center for Strategic and International Studies, a private research group, said in an interview yesterday that short of a total collapse of North Korea, the U.S. military has what it needs to handle the problem.

"The South Korean ground forces are strong enough to handle and deter a North Korean attack on the ground," said Green, who was senior director for Asia on President George W. Bush's National Security Council. "What they need is help with air forces and naval forces, and that is not what we're using in Iraq right now." He sees no shortage of U.S. air and naval power.

Skelton agreed that "we're in pretty good shape" in terms of air and naval forces available for potential Korean duty.

U.S. Defense Secretary Donald Rumsfeld and others argue that even with smaller numbers of U.S. ground troops in South Korea, recent technological advances and improvements in the South Korean army have increased the overall level of military power facing North Korea.

The U.S. Air Force has fighter planes, surveillance aircraft and support planes at two major bases in South Korea and three bases in Japan. It also has been rotating a fleet of long-range bombers to Andersen Air Force Base on Guam, well within range of any target on the Korean peninsula.

The Air Force also has begun basing C-17 long-range transport planes in Hawai'i.