A bipartisan group says the US must strike Iran’s nuclear sites many times ‘over a period of years’ to halt the program successfully.

A recent study conducted by the Bipartisan Policy Center and prepared under the guidance of former senators Republican Daniel Coats and Democrat Charles Robb suggests that the next US president would be wise to make contingency plans for a military attack against Iran.

Contrary to the findings of the UN nuclear watchdog, the US accuses Tehran of pursuing nuclear weapons. In its latest report, the International Atomic Energy Agency announced that it could not find any ‘components of a nuclear weapon’ or ‘related nuclear physics studies’ in Iran.

The release of the Bipartisan Policy Center report comes ahead of the US presidential elections that will see Republican John McCain and Democrat Barack Obama face off on November 4.

Senator McCain says he would intensify pressure on Iran through sanctions before attacking the country – under the pretext that Tehran, a signatory to the nuclear Non-Proliferation Treaty (NPT), seeks nuclear weaponry.

Senator Obama, meanwhile, has promised to engage Iran diplomatically to find a solution to the dispute.

Under US pressure, the UN Security Council has intervened in Tehran’s nuclear case to slap three rounds of sanctions on Iran in spite of the pertinent international organization, the UN nuclear watchdog, having confirming the ‘non-diversion’ of Iranian nuclear activities.

After extensively monitoring Iran’s nuclear program since 2003, the IAEA announced that Iran has managed to enrich uranium-235 to a level ‘less than 5 percent’ – a rate consistent with the construction of a nuclear power plant. Nuclear arms production, meanwhile, requires an enrichment level of above 90 percent.

“A military strike is a feasible option and must remain a last resort to retard Iran’s nuclear development,” reads the bipartisan report.

“However, unless sustained by repeated strikes against rebuilt or newly discovered sites over a period of years, military action alone is likely only to delay Iranian nuclear development while entailing risks of retaliation … which could quickly escalate to full-scale war.”

Iran cites diplomacy as the only means acceptable in clarifying the civilian nature of its nuclear program and has warned that it would not hesitate to take all necessary measures to protect the country should it come under attack.

A realistic retaliation would be for Iran to target US military bases in the oil-rich Middle East, where American forces are in no position, according to Iranian officials, to effectively defend themselves.

In its latest measure to prepare for a potential attack against its soil, Iran appointed the elite Islamic Revolution Guards Corps (IRGC) forces in charge of securing its interests in the Persian Gulf.

Iran has also announced that it is fully monitoring the strategically vital Strait of Hormuz, through which as much as 40 percent of the world’s sea-transited crude oil passes.

Iran says the IRGC could, in times of war, effectively blockade the passage using high-tech weapons systems capable of targeting any vessel within a range of 300 km (185 miles) from Iranian shores.

The Bipartisan Policy Center report comes as Israeli threats against Iran are fueling speculation that either Tel Aviv or Washington may launch airstrikes against Iran before George W. Bush leaves the Oval Office.