The U.S. government today for the first time refused for political reasons to allow Salvadoran leftist rebel leader Ruben Zamora to visit the United States.

The U.S. Embassy here issued a statement saying that a visit by Zamora would not be "appropriate" right now. It noted that Zamora had said during a June visit that his guerrilla movement took full responsibility for the murder of a U.S. military adviser in El Salvador in May and that further killings were possible.

Under U.S. immigration law, Zamora needs a special waiver to visit the United States because he belongs to a group classified as "anarchist, communist or terrorist." Before being turned down today, Zamora had received the waiver 11 times. He had been refused entry on other occasions--most recently, for last month's March on Washington--but only for procedural reasons such as a late application.

Reached by telephone at his home here, Zamora said that he had planned to travel to the United States Sunday or Monday for about two weeks at the invitation of Rep. Jim Moody (D-Wis.) and of the World Affairs Council in Riverside, Calif. He said that several other congressmen also had asked to meet him in the United States.

In Milwaukee, Rep. Moody protested the visa denial as "unfortunate and harmful to American interests." He said Zamora had been invited as a panelist for a conference at the University of Wisconsin, Milwaukee, next Saturday, along with El Salvador's ambassador to Washington.

Zamora expressed bewilderment that he was refused entry after having met presidential envoy Richard Stone in July and August.

As internal coordinator of the political-diplomatic commission of the Salvadoran insurgent alliance, Zamora probably is the rebels' best-known representative in the United States. A former Christian Democratic politician, he is affiliated with the political side of the Farabundo Marti Liberation Front-Democratic Revolutionary Front--known by its Spanish initials FMLN-FDR.

The embassy statement said:

"While we are fully supportive of the widest possible dialogue directed toward bringing the Salvadoran left into a democratic process, the department decision also took into account Mr. Zamora's remarks, speaking as a spokesman of the FMLN-FDR during his June visit to the United States, when he noted that the FMLN took 'full responsibility' for the murder of the deputy U.S. milgroup commander in El Salvador, Lt. Cmdr. Albert Shaufelberger, and warned that 'We can't guarantee that this won't happen again.' "

(In another development, the State Department noted that Carlos Nunez and other members of Nicaragua's Council of State had applied for U.S. visas. The department statement said the visa applications would be "seriously" considered but added pointedly that "serious problems" had forced the cancellation of Assistant Secretary of State Langhorne Motley's planned visit to Managua.