Former United States secretary of defense Robert Gates.

A “better deal” over Iran’s nuclear program that will not “scare [U.S.] allies half to death” has yet to be achieved, but is still possible, contended former Secretary of Defense Robert Gates in an interview with Face the Nation on Monday.

To achieve a good deal, sanctions must be phased out over time “based on performance,” which Gates said was always the U.S. position, and which Iran’s leaders reject in favor of immediate relief.

He said Iran was likely to cheat unless an “on-demand inspection at all facilities, including military facilities” is established.

The former defense secretary said he had “several concerns” over the current framework, which faces a June 30 deadline and needs congressional approval.

Among those concerns, Gates dismissed the idea of an automatic reimposition of sanctions, calling the likelihood of the international community being able to snap back sanctions once they have been lifted, “very unrealistic.”

Gates — who was defense secretary under U.S. presidents George W. Bush and Barack Obama — doubted Obama’s hope that a nuclear deal with Iran would temper the country’s “revolutionary” government.

That is “very unrealistic,” he said.

“[The Iranians] didn’t come to the table out of goodwill. They came to the table because their economy was being strangled and the leadership was afraid they might get overthrown. So they are there because they have to be there,” he said.

Still, the alternative should negotiations fall through is not a war, he said.

Negotiators from Iran, the U.S., U.K., Russia, China, France and Germany and working to finalize a long-term agreement to curtail Iran’s nuclear program by June 30.

Russia rejected the snapback mechanism, with its ambassador to the U.N. saying “there can be no automaticity, none whatsoever.”

Iran’s adversaries in the Middle East, especially Saudi Arabia and Israel, have expressed concerns that an economically emboldened Iran will speed up efforts to extend its influence throughout the region, where they say it already has armed proxies in Lebanon, Syria, Yemen and Iraq.

In 2012, Gates told the Jewish Federation of Greater Philadelphia that a military conflict with Iran would end in “catastrophe.”

Watch a segment of Gates’ comments below: