French President Francois Mitterrand flies here today for a luncheon visit with President Reagan that is likely to center on differences about policy toward the Soviet Union and the handling of leftist governments and guerrilla movements in Central America.

Mitterrand's 10-hour visit, via the supersonic Concorde, is described by officials on both sides as a base-touching mission in advance of the seven-nation economic summit scheduled for Versailles in June.

Undersecretary of State Lawrence S. Eagleburger, speaking to reporters at a breakfast meeting yesterday, sought to discourage speculation that the visit had been hastily advanced because of sudden difficulties between Washington and Paris.

However, Eagleburger mentioned several areas likely to be discussed and on which Paris and Washington differ, including the Soviet natural gas pipeline, economic credits for the Soviet Union, Central American policy, high interest rates and the Middle East.

According to U.S. and French sources, the decision to schedule Mitterrand's visit now rather than later this spring emerged from a mid-February visit to Paris by Michael K. Deaver, one of Reagan's senior White House aides. The visit comes at an important moment in the Reagan administration's policy making on several of the most important issues of the French-American agenda.

Reagan, in National Security Council meetings last week, deferred action on proposals to press the allies to scuttle the planned natural gas pipeline between the Soviet Union and Western Europe.

He took this decision at the behest of Secretary of State Alexander M. Haig Jr., who argued that tough U.S. action on the pipeline issue is likely to succeed only in creating a crisis within the Western alliance.

The French have agreed to supply major financing for the pipeline, despite American opposition, and also have contracted to purchase some of the Soviet gas. Haig said recently that he was "appalled" by the decision of French banks to finance the pipeline following the Soviet support for the crackdown in Poland.

A U.S. delegation headed by Undersecretary of State James L. Buckley is scheduled to travel to Paris, Bonn, London, Rome and Brussels beginning tomorrow to discuss Western economic policies toward the Soviet Union and Poland.

Reagan is expected to consider new decisions in this field following the talks with Mitterrand today and the return of the Buckley mission next Friday.

Forging alliance-wide agreements on economic policies toward the Soviets may be increasingly important in view of the State Department belief, as expressed by Eagleburger, in "a strong likelihood" of new internal trouble in Poland this spring and summer. Such trouble and the Soviet reaction to it could pose new tests of alliance unity in response.

The situation in Central America, where Paris and Washington are openly at cross-purposes, is another potentially vexing point of difference for discussion over the lobster bisque and veal Reagan will offer his French visitor today.

While U.S. officials have been viewing with alarm a military buildup in Nicaragua, France has announced a $16 million arms sale to that country, justified on grounds that this is a useful alternative to Soviet and Cuban sources of military supplies. Washington sharply condemned the French decision.

France, which cooperated with Mexico last year in calling for government-rebel negotiations and an internal political settlement in El Salvador, has strongly endorsed the recent Mexican proposal for a regional political settlement involving the United States, Cuba, Nicaragua and the government and guerrilla forces in El Salvador.

Reagan is giving "in depth" study to the negotiations proposal, according to Haig, but there is no sign that it is likely to be accepted.