SAN FRANCISCO — Conceived as a means of deterring a nuclear strike by the Soviet Union or North Korea, missile defense is proving a useful tool in persuading the Arab countries of the Persian Gulf not to acquire nuclear weapons, according to a former head of US Strategic Command.

Retired Marine Gen. James Cartwright, who also served as vice chairman of the Joint Chiefs of Staff, told the annual gala of the Ploughshares Fund the night of June 8 that members of the Gulf Cooperation Council (GCC), contrary to published reports, are already extensively sharing data on ballistic missile and rocket threats. This sort of sharing, he said, is key to dealing with potential threats from Iran, a country that many GCC states regard as their chief regional adversary and worry will be bolstered by sanctions relief under an impending nuclear accord.

“Strategically,” Cartwright said, missile defense has yet to prove its worth as a tool against an intercontinental ballistic missile. “Tactically, however, missile defense could provide reassurance to our Gulf allies.”

Missile defense, Cartwright added, was a manifestation of “extended deterrence” that could persuade GCC states that they don’t need to develop nuclear weapons to protect themselves against Iran should the Islamic Republic violate the terms of an anticipated long-term nuclear agreement and acquire nuclear arms or simply continue to augment its conventional capabilities.