United Nations, N.Y. — Libyan strong man Muammar Qaddafi has driven a wedge between Ronald Reagan and Francois Mitterrand. The American and French leaders, whose countries have enjoyed some harmony for three years, are experiencing strain over recent developments in Chad, Egypt , Libya, and Morocco.
French Foreign Minister Claude Cheysson travels to Washington this week to clear up disputes with the US, a task considered difficult because of the two nations' different approaches to the third world.
The trouble started when President Mitterrand made a secret trip to Morocco in September and appeared to sanction a treaty calling for unity between pro-West, conservative Morocco and radical, pro-Soviet Libya, signed in August.
Colonel Qaddafi and King Hassan II - who had been mortal enemies - thus suddenly became political pals. Many observers considered the agreement a tactical move by both North African leaders.
In the treaty, Libya agreed to end its support of Polisario rebels seeking to end Moroccan rule over Western Sahara. King Hassan in turn partially helped Qaddafi extricate himself from diplomatic isolation.
Morocco agreed to help mediate a mutual withdrawal of French and Libyan troops from Chad. After this double pullout, Mitterrand and Qaddafi were to meet. For Qaddafi, public recognition by one of the West's major leaders was crucial.
After last spring's terrorist incident in London in which a British policewoman was killed by shots fired from within the Libyan embassy, Qaddafi's image sank to an all-time low. He had reason to believe that attempts to overthrow him might be undertaken with Western support.
Last week both the Libyan and French governments officially stated that they had taken all their troops out of Chad. The US vigorously denied that all Libyan troops had actually left Chad and offered to show satellite pictures to support that claim.
Nevertheless, Mitterrand flew to Crete, where he met with Qaddafi.
''For Qaddafi, this meeting was a tremendous plus. He was handed respectability,'' says a West European diplomat whose country played a role in mending fences between France and Libya. ''For Mitterrand it could have been a plus but turned out to be a minus since French political opposition and the press strongly criticized his move and called him naive for trusting Qaddafi.''
A high-ranking French diplomat elaborates on how the US and France differ in approaches to Qaddafi as well as theirdivergent interests in Africa:
''Reagan tends to treat all third-world problems as part of the global East-West contest,'' he says. ''France prefers to deal with them on a regional basis and to isolate them from big-power rivalry. Beyond that, France has strategic, economic vital interest in North Africa and in black Africa. More often than not, the US acts as a rival and as a competitor rather than as an ally in this part of the world.''
US-French strain regarding Libya can be summed up as follows:
When France sent troops into Chad in 1983 to stop Qaddafi's brigades from overrunning the former French colony, the US offered France the assistance of sophisticated radar planes to monitor Libyan activities. The offer was politely turned down.
France did not use its power to push farther north and get the Libyans out of Chad. It settled for a compromise, stopping at a line that cut the country in two.
''By striking a deal with Qaddafi through Hassan, Mitterrand is seen as having made a fool's bargain,'' says a US diplomat.
''Qaddafi has reneged on many such deals and is expected to try to exert his rule in Chad, using it as a springboard for destabilizing Nigeria, Sudan, Niger, and the Central African Republic.''
The French agree with this assessment but, says a French diplomat in private: "We have no illusions about Qaddafi, but we don't think that he is merely a Soviet stooge [as the US does.] We are in Chad to protect that country's independence and to shield French-speaking African countries south of Chad.
"Furthermore, the troops that we pulled out of Libya are now based in Cameron and may be brought back into Chad at a moment's notice."
Finally, we have not been overly impressed by US behavior as an ally in Lebanon. Considering the lack of US staying power in situations that stir a controversy in the US, we prefer to act alone."
A highly placed French source says that neither France nor the US puts its money where its mouth is when it comes to Libya.
He adds: "Mitterand wants to preserve considerable French oil interests and arms sales to Libya. Being on good terms with Qaddafi, he also hopes to get major contracts for French companies to construct a canal from the sub-Saharan desert to the Mediterranean and huge irrigations systems, plus trade in liquefied natural gas. The French companies involved might then support him in legislative elections in 1986. Furthermore, it would be advantageous politically for him to be able to show his countrymen that he has settled the Chad problem without a financial burden to France."
To be fair, the official adds that while the US calls Qaddafi "the world's leading terrorist," three US oil companies continue to operate in Libya, helping to support Libya's economy; and, a few years ago, five former US intelligence and military agents were able with surprising ease to smuggle military equipment out of the US and into Libya to help Libyan terrorists.
While Reagan sent Gen. Vernon Walters to see Hassan in September to express US concern over Morocco's agreement with Libya, the US apparently exerted none of the pressures that it could in order to turn Hassan around, continues the high French official. After all, the US is providing Morocco with substantial economic and military aid.
Morocco is the US's closest ally in North Africa, the French official says, and yet the US does not really seem to mind Hassan's partnership with Qaddafi. "So to say the least there seems to be a good deal of hypocrisy coming out of Paris and Washington with regard to Libya. And neither the French nor the Americans are in a position to play 'holier than thou' in this instance.
Moderate African countries, meanwhile, are worried. They wonder how the US can live with the Morocco-Libya pact.
The unveiling of a Libyan assassination plot against a former Libyan official living in Egypt is aimed at embarrassing Mitterand, who has just sat down with Qaddafi, says the French official.