Chad's president, Hissene Habre, joined senior French officials today in expressing optimism that Libyan troops would pull out of his war-torn country despite indications that a Franco-Libyan agreement on mutual troop withdrawal already might have run into trouble.

The Chadian leader's remarks came at a brief meeting with reporters following a "minisummit" here with French President Francois Mitterrand and the heads of state of three moderate, French-speaking African countries. The comments appeared to mark a distinct change of tone from earlier expressions of skepticism in the Chadian capital, Ndjamena, about the likelihood of a Libyan withdrawal.

France and Libya have set mid-November as the target date for completing the withdrawal of their troops from the landlocked African state. The French troops were sent to Chad in August 1983 to stop an advance by Libyan-backed rebels from the north that threatened the Habre government.

The Franco-Libyan agreement, which was negotiated personally by the Libyan leader, Col. Muammar Qaddafi, and senior French officials, envisaged sending neutral observers to Chad to ensure that both sides withdraw. So far, however, this part of the agreement has not been carried out.

Insisting that the deal had been concluded without his approval, Habre has refused to accept observers from the Soviet-leaning "people's democracy" of Benin on behalf of the Libyans. Libya, in turn, refused to accept observers from Senegal, a generally pro-western state, who were to monitor the agreement on behalf of the French.

Following his meeting with Mitterrand, Habre refused to say whether he would now accept the observers from Benin.

French officials have said that they have little faith in the observers and intend to rely on electronic eavesdropping and overflights to see whether the Libyans are leaving. According to reports from Chad, the French withdrawal -- which had been due to get under way in phases beginning on Sept. 25 -- has been delayed pending firm evidence about Qaddafi's intentions.

Speaking on the steps of the Elysee presidential palace, Habre said that he assumed that the Libyans would respect "the commitment that they have undertaken to withdraw" from northern Chad.

His optimistic comments echoed remarks by French Foreign Minister Claude Cheysson, who told the foreign affairs committee of the National Assembly that the Libyan withdrawal was being conducted slowly but under "reasonable conditions." Cheysson was the French official primarily responsible for negotiating the agreement with Qaddafi.

Intelligence reports from Chad have spoken of apparently disorganized Libyan troop movements between west and east with no sign yet of a general withdrawal toward the north.

French officials said they expected Mitterrand to use today's meeting with Habre to urge the formation of a national unity government in Ndjamena including representatives of rival factions in Chad's long-running civil war. They added, however, that France had no interest in playing the role of mediator in Chad's internal political crisis.

Other African heads of state taking part in today's meeting were Presidents Mobutu Sese Seko of Zaire, Omar Bongo of Gabon and Felix Houphouet-Boigny of Ivory Coast. All three leaders were staunch supporters of the French military intervention in Chad last year. Zaire still has troops stationed in Ndjamena.

French officials indicated that they would be prepared to step up economic assistance to Chad, giving them possible diplomatic leverage over Habre. The minister for cooperation and development, Christian Nucci, announced that France would send 20 tons of medical supplies, 40 tons of food products and cloth, and up to 300 tons of grain to areas of central and southern Chad that have been struck by famine.

France is also likely to increase its military assistance to Habre's 4,000-man Army, which generally is considered to be better trained and equipped than the rebel forces led by former Chadian President Goukouni Oueddei.