The latest tool of Rep. Wayne Owens, D-Utah, to pressure President Bush to support a ban on all nuclear tests is a letter he initiated last week that included signatures of 31 powerful House members.

Signed by such people as House Foreign Affairs Committee Chairman Dante B. Fascell, D-N.Y., and House Interior and Insular Affairs Committee Morris Udall, D-Ariz., the letter asked the administration to support a test ban to help stop the spread of nuclear arms.Owens has also introduced a House resolution and held a press conference at the United Nations saying a test ban would help stop the development of more nuclear weapons worldwide.

For three more days in New York, an international conference is meeting to consider amending the Limited Test Ban Treaty of 1963 to ban underground nuclear tests, such as those now conducted at the Nevada Test Site.

While the Soviet Union is backing that proposal, the United States and Great Britain have threatened to veto it if it is adopted - virtually ensuring its death.

The letter from Owens and the other representatives Monday said, "Iraq's aggressive campaign to develop nuclear weapons, coupled with its demonstrated willingness to use weapons of mass destruction in its arsenal, underscores the vital necessity for American leadership in combatting nuclear proliferation."

It added, "Continued opposition to a Comprehensive Test Ban jeopardizes the future of the nuclear Non-Proliferation Treaty, which must be extended in 1995."

The members of Congress that signed Owens' letter also said backing a total test ban "offers a chance for the United States to assume a proper leadership role in efforts to contain the spread of nuclear weapons."

The letter was also signed by powerful Democratic and Republican members of the Appropriations, Ways and Means and Judiciary committees.