The Carter administration has decided to supply Morocco with Maverick missiles to go with American fighter-bombers to be delivered later this year.

The sale, disclosed yesterday by State Department sources, is another boost in U.S. support for King Hassan, considered one of the more moderate and friendly Arab leaders.

He has been fighting a guerrilla war for control of the Western Sahara for four years against the Algerian-backed Polisario Front guerrillas.

The sources, who asked not to be identified, said the air-to-surface Maverick rockets were unlikely to be used in that conflict since they are expensive and designed primarily to knock out tanks and radar sites.

The Mavericks which cost about $50,000 apiece, would be attached to the 20 F5 fighter-bombers the administration decided last October to sell to Morocco.

That $232.5 million deal also included six OV10 reconnaissance planes and 24 helicopters for use against the guerrillas.

Congress allowed the sale to go through, but called on the administration to tie delivery of the weapons to progress on negotiations between Morocco and the Polisarios, who are challenging Morocco's annexation of the Western Sahara.

Since the total cost of the Mavericks is less than $7 million, there is no way under the law that Congress can veto the deal.

U.S. policy for nearly 20 years has been to supply Morocco with defensive weapons only. State Department officials claimed that last October's decision was consistent with that policy.