Paris — President Francois Mitterrand's Socialist government is planning to build up its nuclear strike force at the expense of conventional weapons.
This policy puts French military thinking at odds with the rest of the Western alliance, which is leaning toward modernizing conventional arms. The shift worries American diplomats, who fear it might erode allied support for larger military budgets. And it promises to throw up a domestic political storm here.
During its first year in office, the Mitterrand government increased military spending on both nuclear and conventional weaponry. Today, with a large budget deficit it can no longer afford to do this.
To help reduce the budget gap, the government is trimming 13.4 billion francs ($1.9 billion) from 1982 military expenditures. Orders for 25 Mirage 2000 fighter bombers, 47 AMX-10 tanks, and 26 155mm artillery batteries have been canceled, and production of a new navy antisubmarine aircraft delayed.
But the 20 percent of the 1982 budget spent on nuclear weapons is not being touched.
The 1983 military budget continues this pattern. Nuclear procurement funding will be increased 14 percent, nuclear research-and-development funds will grow by 21 percent, and spending on nuclear missile-firing submarines will be raised by 26.2 percent.
Financing for the conventional forces will grow by only 8 percent - a real decrease or at best no real increase after inflation.
French Defense Ministry officials argue that the buildup of the infantry, armor, and artillery corps under former President Valery Giscard d'Estaing makes a zero-growth budget for 1983 acceptable.
Critics disagree. ''It's a bad budget,'' said Pierre Lellouche, director of studies at the French Institute for International Relations. ''We were not up to the German Army in training or arms even before this budget, because we are using so much money to finance our nuclear program.''
Mr. Lellouche and other critics fear that further cuts are scheduled after 1983. The Socialists must present a detailed military plan for the years 1984 to 1988 next spring, and the daily Le Monde has reported the government is thinking of reducing France's land forces by as much as 10 percent, or 35,000 men.
Defense Ministry officials deny this. ''No final decisions have been made,'' an official insisted.
But he admitted that if military funding continues on the overall no-growth pattern set in 1983, ''choices will have to be made.'' And the Socialists' preference for nuclear weapons is clear.
By the 1990s, France plans to increase its fleet of nuclear submarines from five to seven, create a mobile land-based missile force, and develop longer-range and multiple-warhead nuclear missiles.
''Anyone who tells me he prefers one more division of soldiers to a missile-launching nuclear submarine,'' Defense Minister Charles Hernu has said, ''is living in the wrong age.''
This thinking runs against current NATO strategy. Gen. Bernard Rogers, NATO's supreme commander in Europe, recently called on allied governments to spend an extra $14 per capita over the next six years to give NATO enough conventional armaments to hold back a Soviet assault without resorting to nuclear weapons.
American diplomats here worry that an emphasis on nuclear arms may estrange France from this new NATO defense posture. Any troop reduction, especially any move to thin out the 50,000 French troops deployed in West Germany, would put pressure on the other allies to increase their front-line forces.