Paris — Sharp differences over the deteriorating situation in Central America are expected to be aired in full March 12 when French President Francois Mitterrand flies to Washington to meet with President Reagan.
''Our priority issue will be Central America,'' one American diplomat said. His assessment follows the recent warnings by the American ambassador, Evan Griffith Galbraith, that Central America is now the major point of contention in Franco-American relations.
It is not publicly known exactly who advanced the Mitterrand-Reagan meeting from its original date in May. The meeting was originally planned as a prelude to the June economic summit at Versailles. Although US officials would not elaborate on the scheduling, it is understood here that the Americans sought to have the trip pushed up because of increasing tension over Central America.
In an interview published this week, Ambassador Galbraith rebuked the Mitterrand government for its outspoken stand against American policy in Central America, which he called ''short-sighted.''
France has been urging diplomatic recognition for the Salvadoran guerrillas and has sold a limited quantity of ''defensive'' arms to Nicaragua.
At the same time, the French want to turn the Mitterrand-Reagan conversation toward economic matters. ''We see the economy as the major topic of discussion, '' one French Foreign Ministry official said.
Mitterrand is likely to press his case that high American interest rates are at the root of the Western recession and friction in the Atlantic alliance. Recently, French Foreign Minister Claude Cheysson pointed to ''high US interest rates'' as ''the area where I fear we will see the greatest difficulties between the United States and the Europeans.''
But American officials here said that there will not be much time left for economics in the short four-hour meeting between them after Central America is discussed.
That is because, as once American official said, ''we have a lot of persuading to do on Central America.'' The French are standing firm in supporting the Salvadoran guerrillas as genuine social democrats battling a corrupt oligarchy. They support the recent peace initiative of Mexican President Jose Lopez Portillo, calling for a negotiated solution to the war.
And the French defend their arms sales to Nicaragua as providing an ''alternative'' to forcing the Sandinistas to rely exclusively on the Soviet Union and its allies for weapons. Such sales can provide a moderating influence on the Sandinistas, the French argue.
Ambassador Galbraith said the French don't understand how vulnerable the various liberation movements in Central America are to Soviet and Cuban influence.
He pointed to Nicaragua as proof, which he said was being turned into ''a major base for revolutionary activities throughout the region.'' He argued that French arms would not moderate the Sandinistas, and insisted that Nicaragua was a ''totalitarian country'' which abuses human rights.
In simple terms, one American diplomat here explained, ''we want to show them that Nicaragua poses a real threat and that the best hope for El Salvador is in the upcoming elections.''
The US official said President Reagan would try to get Mr. Mitterrand to ''express some understanding for the (Jose Napoleon) Duarte government'' as well as gain French assurances that there would be no further arms sales to Nicaragua.
In addition, Reagan will try to obtain French assistance with his recently announced Carribean Basin initiative. ''At the very least we would like him to endorse it,'' the American said, adding, ''we would like even more for the French to contribute financially.''
Mr. Mitterrand may very well promise to try to push the European Community to offer more financial aid to the Carribean, a French Foreign Ministry official said.
At the same time Mr. Mitterrand made this statement, however, he reiterated his opposition to Washington's general policy directions in Central America.
With tensions so high over Central America, the other major bone of contention between France and the US - the Russian natural gas deal - may not get much of a hearing.