TEHRAN (Reuters) - The United States could unleash vastly superior firepower if it attacked Iran but Tehran could strike back against its forces in Iraq and threaten oil supplies crucial to the world economy.

Washington says it is committed to resolving the crisis over Iran's nuclear program diplomatically.
""It should be a walkover militarily,"" said London-based defense analyst Andrew Brookes about any U.S. attempt to knock out the Islamic Republic's atomic installations.
""The hard bit is what comes afterwards and that is opening Pandora's Box,"" said Brookes of the International Institute for Strategic Studies (IISS) think-tank.
Iran's confidence has grown as it watched America's failure to get a grip on Iraq despite its overwhelming military supremacy.
Iran says that the West would regret any attack, warning of a ""quagmire deeper than Iraq.""
""Iran can not win a military campaign in a conventional sense but what it can do is cause considerable amount of grief afterwards,"" Brookes said.
Tim Ripley, a defense analyst who works for Jane's Defense Weekly, said Iran's armed forces had shown resilience during their 1980s war with Iraq and the nightmare scenario for Washington would be launching a war it could then not finish.
The United States had the capability for another ""shock and awe"" campaign but fighting Iran would not be like the U.S.-led invasion of Iraq in 2003 and parts of the Iranian military would likely ""put up a real good fight,"" he said.
""If you compare like for like the Iranians may not be as good as the Americans but their leadership ... know how to use what they've got to really great effect,"" Ripley said.
He said Iran could simply declare the Strait of Hormuz at the entrance of the Persian Gulf a war zone to send oil prices, already nearing $100 a barrel, soaring without a shot being fired.
One Western expert said Iran's military was in a better state ""than people give it credit for"" with good technology and equipment including Russian anti-aircraft missile defense.