The Spanish government appears unwilling to sign a contract to purchase 72 U.S. F16S for an estimated 1.5 billion unless components for the advanced General Dynamics Jet fighter are made in Spain.

Informed U.S. and Spanish sources have confirmed that the deal - spelled out in a complex section of the bilateral U.S.-Spanish treaty signed nearly two years ago - is serious trouble.

The unannounced difficulties between Washington and Madrid over the F-16S seem to have raised French hopes that the Spanish air force will buy 31 French Mirage F-1-M36S for approximately $136 million. The advanced Mirage is the American jet's main foreign competitor in the world's lucrative warplane market.

As part of its sales drive, France reportedly is prepared to produce F-1 parts in Spanish factories to provide employment for the depressed Spanish economy. The Spanish air force already has an estimanted 70 Mirages of various types in service. Most Spanish military aircraft, however, are American.

General Dynamics, according to U.S. aircraft industry sources here, cannot contract to make F-16 components in Spain. Without the approval of the U.S. government.

U.S. sources indicated that unless Spain signs a "letter of offer" for the F-16S in the near future, General Dynamics will not be able to deliver the aircraft by 1982 Spain has also been told that a protracted delay will mean higher prices, sources said.

There is no question that the warplane agreement has been the object of intense talks, but neither U.S. or Spanish officials are willing to discuss differences in detail or for direct attribution.

Coproduction is clearly one of the points separating thefever. Madrid wants to bolster Spanish arms production to help both employment and Spanish technical capabilities.

Spain opted for the F-16s when the treat was signed in anticipation of eventual entry ito the North Atlatic Treaty Organization. The General Dyamics plane had been favored over the Mirage by several NATO countries in the hard-sell competion between the United States and France.

Despite its old military relationship with Spain, however the United States does not seem willing to cooperate on production of the F-16. The United States appears to prefer to sell finished weapons old or new.

The U.S. attitude has left the wayopen forthe French, who have been big sellers of weapons to Spain including tanks, submarines and rockets in addition to Mirages.

To strengthen their sales positions, the French have made arrangements for the manufacture in Spain of 200 French AMX 30 taks for the Spanish army, and for the construction of French submarines for the Spanish navy in Spanish shipyards.

Apart from the current French Mirage campaign, France and Spain are currently negotiating a deal for Spaish manufacturer of the French Pumahelicopter under license.