The United States has sent two AWACS planes to Egypt to practice combat operations ranging from directing fighter-bombers to their targets to helping ships set up a blockade, administration sources disclosed yesterday.

The AWACS planes, together with their supporting group of 250 Air Force personnel, establish a precedent for that kind of U.S. military presence when trouble breaks out in the Middle East, officials said.

Beyond establishing that precedent, which officials described yesterday as highly significant, the presence of the two AWACS planes and their crews in Egypt gives President Carter greater confidence of success should he opt for military action against Iran.

The AWACS -- standing for airborne warning and control system -- is the most sophisticated plane in the sky for warning of enemy attacks or directing combat operations from overhead.

It can spot an enemy plane flying in low from 200 miles away, for example, and direct friendly fighter aircraft to intercept it. This ability would help aircraft carriers and surface ships off Iran, if the crisis there escalates to armed conflict.

The advanced radars, computers and communication inside AWACS could help Egyptian planes protect that country's borders, if the United States and Egypt move to coordinate their air forces.

The two AWACS in Egypt, sources said, are equipped to communicate with U.S. warships off Iran, which would assist Carter should he attempt a blockade on ship traffic in the Persian Gulf, the sea lane for Iranian oil and other goods.

However, in citing this capability, officials did not indicate that any military action against Iran was imminent. Instead, they said the planes were sent to Egypt to establish a precedent and to rehearse for several contingencies.

Israeli officials broke the news of the American planes operating in Egypt, administration officials said. The Egyptian government followed up yesterday with a formal announcement of the planes' presence.

Neither the Egyptians nor the State Department would indentify the kind of planes or what base they were operating from. Other sources said the two AWACS have been in Egypt for three weeks.

The usual crew for an AWACS is four to fly it and 13 technicians to operate and monitor its complicated gear. Presumably, several crews went to Egypt so they could be rotated for training and relief.

The Egyptian government has offered the U.S. military temporary use of its air bases. The Pentagon is putting itself in position to make use of this offer at the same time it is seeking temporary or permanent use of ports and airfields in such other countries as Kenya, Somalia and Oman.