Peru has notified the Reagan administration it is interested in buying 26 General Dynamics F16 fighter-bombers, government officials said yesterday. Such a sale could mark a significant shift away from Peru's past dependence on Soviet weaponry.

It would also constitute the first sale of a warplane designed expressly for developing countries under the FX program begun by former president Carter and embraced by President Reagan. The FX program is designed to satisfy Third World demand for hotter fighters without selling planes that are so advanced that they would upset the arms balance in a region.

The F16 Peru would get would have about 20 percent less range than the version flown by the U.S. Air Force. The biggest difference is that the FX is powered by the older J79, General Electric engine, the powerplant for the F4 fighter-bomber, rather than the higher performance Pratt & Whitney F100 in the F16.

Government officials familiar with the processing of Peru's request, which now goes from the Pentagon to the State Department, predicted Reagan will welcome the chance to broaden the U.S. arms supply relationship with the Latin American country, especially if it comes at the expense of the Soviet Union. They said talks on the F16s, however, are still in the preliminary stage.

Peru caused consternation among Washington officials in 1976 when it announced it was rejecting a U.S. offer of Northrop F5 fighters and buying 36 Soviet SU22 fighter-bombers instead, becoming the first Latin American country outside of Cuba to make such a purchase of Soviet warplanes.

French Mirage jets had been the mainstay of the Peruvian air force until that time.

Asked if the poor performance of Soviet weaponry in the fighting in Lebanon prompted Peru to turn back to the United States, government officials said they doubted the choice of the F16 was made that recently. In the Lebanon conflict, Syrian planes supplied by the Soviet Union were clobbered by Israeli aircraft built by the United States.

In the battle for the Falkland Islands between Britain and Argentina, Peru was suspected of supplying equipment to the Argentines. This could be a factor as the Reagan administration weighs the Peruvian request for F16s. Peruvian forces, however, were not directly involved in the Falklands fighting.

The F16/J79 combination would give Peru a supersonic plane for dogfighting and for ground attacks.

The plane carries Sidewinder heat-seeking missiles for air-to-air combat and up to six 500-pound bombs for ground attack. Its combat radius, meaning out to the target and return, is about 500 miles, compared to about 700 miles for the U.S. Air Force version of the F16.

Each plane costs about $15 million, although a deal with Peru would probably include training and spare parts, pushing the package price upward.

Carter, on Jan. 4, 1980, lifted his ban on selling foreign nations weapons that were not already in the U.S. inventory, allowing arms makers to design planes for sales abroad.