Britain gave a cautious welcome today to Soviet leader Mikhail Gorbachev's latest arms control proposals but stressed that negotiations involving its nuclear deterrent force could only commence after Moscow and Washington agreed on radical cuts in their massive nuclear arsenals.

British Foreign Secretary Geoffrey Howe, at a press conference ending a two-day visit here, expressed satisfaction that the Soviet Union was putting forward new positions on arms control "that must be given serious consideration."

During his current visit to Paris, Gorbachev has made public a proposed 50 percent cut in U.S. and Soviet strategic nuclear weapons linked to a ban on the militarization of space. He has also proposed separate negotiations with France and Britain covering their independent nuclear forces so that European-based missiles might be curtailed.

While French President Francois Mitterrand rejected the offer today, Howe said Britain would consider such a forum once Moscow and Washington agreed to radical cuts in their strategic forces.

Howe emphasized the "huge differences in scale" between the French and British deterrent forces and the 50,000 nuclear weapons of all kinds now estimated to be deployed by the two superpowers.

Howe said Britain had not yet received any formal proposal to open negotiations with Moscow, but he contended that Britain was prepared to review its nuclear forces after a reduction in U.S. and Soviet arsenals "to see how best we can contribute to arms control."

West German Foreign Minister Hans-Dietrich Genscher, who discussed the Soviet proposals with Howe today, described Gorbachev's offer as "interesting" and worthy of careful scrutiny by the West.

Genscher believes "it is now necessary for the West to contribute to a useful discussion at the arms control negotiations by responding with its own proposals," a Bonn Foreign Ministry spokesman said.

In London, government officials said that Gorbachev's pronouncements in Paris carried a "high public relations content" that could be designed chiefly to sow discord between the United States and its European allies.

Disarmament specialists said Britain's small submarine-based deterrent could not be fairly compared with the Soviets' triple-warhead SS20 mobile land-based missile.

In the Hague, a Defense Ministry spokesman said that the Dutch Cabinet decided today not to take part in the U.S. Strategic Defense Initiative, but would be happy to see Dutch companies involved in SDI research, Reuter reported.