France and Pakistan agreed yesterday to resume negotiations on the French nuclear reprocessing plant under construction in Pakistan. It seemed that the contract might be canceled over French demands to convert the project to make impossible the manufacture of nuclear devices.

A representative of Pakistani leader Gen. Mohammed Zia ul-Haq called on French President Valery Giscard d'Estaing yesterday with a letter designed to resume contacts on the matter.

Giscard has sent Zia a letter in August which the Pakistani military ruler publicly dismissed as "a lemon." It was widely but incorrectly reported at the time as a French cancellation of the contract.

What Giscard in fact proposed was that the projected nuclear reprocessing plant, capable of producing pure weapons-grade plutonium manufactured as a byproduct of enriching uranium for power planst, coprocessing produces "dirty" plutonium mixed with uranium that is unsuitable for atomic arms.

The initial Pakistani reaction was interpreted by many observers as proof that the Pakistani, despite all denials, were actually interested in the project to develop a nuclear weapons capability to match that of neighboring India.

The French government has since blocked export licenses for most of the plant's equipment.

The Pakistanis objected that Giscard's proposal would involve radiacal redesign of the plant and tearing up a large proportion of what had already been built. They also said that the coprocessing technique has not yet been perfected and that U.S. experiences with it elsewhere prove that it is not ready for commercial application.