NATO nuclear experts are recommending the alliance approve U.S. development of a new short-range missile while putting off the thornier decision on deploying it in Europe, diplomats said Tuesday.

The sources said NATO defense ministers would consider the recommendation when they meet in Brussels April 19 and 20 for a session of the Nuclear Planning Group.NATO's plans to modernize its short-range nuclear systems, particularly its force of aging Lance missiles, have caused problems in the Alliance with key ally West Germany reluctant to make a major decision.

West Germany, which deploys most of NATO's 88 Lance launchers and has to contend with a strong domestic anti-nuclear lobby, wants NATO to postpone a commitment to modernize until after national elections at the end of 1990.