Further, the Institute for Science and International Security said in a report, a surprise attack could strengthen Tehran's resolve to acquire the nuclear arms, the Washington Post reported.

The analysis said it found Iran's uranium facilities too widely scattered and protected to be effectively destroyed by warplanes and any damage could be quickly repaired.

"Following an attack, Iran could quickly rebuild its centrifuge program in small, easily hidden facilities focused on making weapon-grade uranium for nuclear weapons," principal author David Albright, ISIS president and a former U.N. weapons inspector, said.

The study is set for release Friday. It says comparisons between a possible Iran airstrike and the Israeli destruction of Saddam Hussein's Osirak reactor in 1981 aren't valid. The 1981 incident dealt a crippling blow to Iraq's nuclear hopes, but, it said, the Iranian program is much better protected and wouldn't be vulnerable to elimination in a single blow, the Post said.

Despite heavy fortification, the huge, subterranean Natanz uranium enrichment plant, the core of Iran's program, could be heavily damaged in an airstrike but the centrifuges could be replaced rapidly, perhaps in hidden underground facilities, the report said.

"Iran would likely launch a 'crash' program to quickly obtain nuclear weapons," Albright told the Post in an interview.