Israel's bombing of Tunisia derailed a carefully crafted U.S. plan to supply arms to Tunisia in exchange for Navy use of bombing ranges in that country and other bilateral military cooperation, according to Defense Department officials.

Adm. James D. Watkins, chief of naval operations, went to Tunisia in the first week of September to discuss with his counterparts some of the detailed arrangements, officials said, only to have the entire arrangement postponed Oct. 1 when Israeli bombers struck the headquarters of Palestine Liberation Organization Chairman Yasser Arafat about 20 miles south of Tunis.

The Pentagon had planned to send a team to Tunisia to assess that country's defense needs, officials said, and anticipated that anti-aircraft radar and missiles would be among items most needed to defend against possible attack by Libya.

The effort to arm Tunisia will be resumed after a cooling-off period, one Pentagon official said. "The plan has been put on ice, not canceled," another said.

The Reagan administration sees Tunisia as a friend and Libya as a threat in the troubled region. That sparked mutual interest forming the foundation for a broad package of military assistance, a defense official said.

The Navy's interest in the Tunisian bombing range stems from lack of instrumented facilities for practice involving aircraft carriers on long deployments in the region, officials said. Navy leaders have been interested in using Israeli bombing ranges, but administration officials have said this would offend Arab nations, and turned toward Tunisia.

Under the aid plan being crafted when Israel bombed the PLO headquarters, the United States would fund modernization of the Tunisian bombing range in exchange for its use.

Israeli bombers flew the 1,500 miles to Tunisia virtually undetected, administration officials said, raising questions about the effectiveness of warning radars in Tunisia, neighboring countries and on U.S. and Soviet warships.

U.S. Navy officials, asked why they did not warn Tunisia of the attack, said no ships along the attack route detected the Israeli approach. Pentagon sources said Soviet warships off Libya apparently failed to detect the Israeli planes.

Administration officials said Italian radar stations may have detected the attacking force of eight Israeli F15s.

The F15s, usually used as fighters, were refueled shortly after takeoff from Israel by modified versions of the Boeing 707 transport. The Israeli F15s, sources said, bunched after the refueling operation and flew that way along a commercial airline route.

Israel apparently tried to disguise the attacking force as a single commercial airliner at the usual altitude of about 35,000 feet, administration sources said. Such a tight formation, officials said, would probably look like a single plane on long-distance radar.