French Defense Minister Charles Hernu and his armed forces chief of staff flew to Chad for talks with President Hissene Habre today, and France resumed reconnaissance flights over its former African colony less than 48 hours after acknowledging that Libyan troops are still in the country in violation of a mutual withdrawal agreement.

French Foreign Minister Claude Cheysson, meanwhile, reiterated, before leaving for an official visit to Washington, that France will match any Libyan troop presence in Chad with its own forces.

Cheysson also attacked what he said was a U.S. press campaign designed to pressure France into hardening its attitude toward Libya, Agence France-Presse reported. Cheysson said the U.S. government may have been using the press indirectly to pressure Paris into "acting toward the Libyans like the Americans act toward Nicaragua."

The developments here came as Egyptian President Hosni Mubarak, speaking a day after Egypt disclosed a Libyan plot to assassinate an exile leader in Cairo, denounced Libyan leader Col. Muammar Qaddafi as "an international terrorist" and urged other countries to take steps to "stop him." Details on Page A14.

The French moves followed political consultations at the Elysee Palace between President Francois Mitterrand and his military advisers on how to respond to the apparent bad faith of Qaddafi. Mitterrand acknowledged Friday that about 1,000 Libyan troops were still in northern Chad despite official French and Libyan announcements on Nov. 10 on the completion of "evacuation operations."

Mitterrand's public admission followed talks Thursday with Qaddafi on the Greek island of Crete and a series of official French statements insisting that the Libyans had left. Mitterrand's handling of the affair was described today by the authoritative French newspaper Le Monde as the Socialist government's "biggest foreign policy gaffe" since it came to office in May 1981.

The independent leftist newspaper Liberation commented in an editorial yesterday that "the city fox" -- Mitterrand -- appeared to have been outwitted by the "desert fox" -- Qaddafi.

Revelations last week by the U.S. State Department and Chad that Libyan troops were still in northern Chad transformed what would otherwise have been a significant foreign policy success for Mitterrand into a major setback. French leaders now tacitly acknowledge that they were aware all along that the Libyan withdrawal was not total -- at the same time that official French spokesmen were claiming that it was.

About 5,000 French troops were sent to Chad in August 1983 to prevent the overthrow of the prowestern government of Habre by Libyan-backed rebels from the north of the country. A formal agreement to withdraw both Libyan and French troops was negotiated by Cheysson in September of this year.

Asked today whether French troops would now be sent back to Chad, Cheysson replied: "We have to wait and see. Nothing can be ruled out." He said the government stood by an earlier statement that "if they the Libyans stay, we stay, if they come back, we come back."

The French delegation that flew to Chad today, led by Hernu, included armed forces chief of staff Gen. Jeannou Lacaze.

According to French intelligence reports, referred to by Mitterrand in a statement Friday, about 1,000 Libyan troops remain in northern Chad -- roughly 20 percent of the original Libyan troop strength there.

The continuing Libyan presence in northern Chad, according to French analysts, appears to be largely defensive. Its principal purpose seems to be to thwart any attempt by Habre's government to retake rebel-held territory.

French officials have rejected criticism in the United States of Mitterrand's decision to meet with Qaddafi by depicting it as hypocritical. Government spokesman Roland Dumas insisted last week that many more Americans than French citizens were in Libya, working on oil-related business.