FACTBOX: What could Iran do if pushed in conflict?

(Reuters) - The U.S. military could unleash superior military force if it attacked Iran over its nuclear program but analysts say Washington may struggle to prevent Tehran from hitting back in Iraq and threatening oil supplies.

Following are some tactics Iran could employ, including unconventional or so-called "asymmetric" methods that have either already been used by Iranian forces or blamed on Iran in the past:

HIT-AND-RUN RAIDS IN THE GULF

During Iran's 1980s war the two OPEC states sought to knock out each others oil exports, Iran's military mounted hit-and-run raids on oil tankers and other shipping in the Gulf. Experts say the Revolutionary Guards, the ideological wing of Iran's military, were a driving force in developing such tactics, often involving small speedboats mounted with a missile and which would stand a better chance of evading detection until the last minute. The Revolutionary Guards has already warned its "martyrdom-seeking" volunteers could cause havoc in the strategic Gulf waterway, if the need arose.

STRIKING U.S. INTERESTS

Supreme Leader Ayatollah Ali Khamenei has said Iran would strike U.S. interests in the region if pushed. Iran's military has declared that they have missiles that can sink "big warships" and others with a range to hit targets across the Gulf, which could include U.S. bases in Qatar and Bahrain, though military experts say U.S. anti-missile defenses could stop such rockets. Outside the Gulf, the United States has blamed Lebanon's Iranian-backed Hezbollah for the 1983 bombing of its marines barracks in Beirut that killed 241 soldiers. Iran's longest range missile, the Shahab 3, can reach Israel.

VIOLENCE IN IRAQ

The United States accuses Iran of backing militants in Iraq, although Tehran denies this. Some Western diplomats say Iran appears to have imposed at least some restrictions to prevent weapons flooding across the border into Iraq, in part because ultimately Iran wants a stable neighbor. But they say, if it came under pressure, Tehran could quickly make the border porous and add to problems for U.S. troops trying to quell violence. U.S. officials say Iran is using rogue elements in the Mehdi Army, led by firebrand cleric Moqtada al-Sadr, to weaken the Iraqi government and boost its influence. Iran has historical ties with Shi'ite Muslim groups in Iraq's government because some of their leaders were exiled in Iran, but analysts say it is unclear if Tehran now holds much sway over policy.

DESTABILISING AFGHANISTAN

Iran says it wants a stable neighbor to its east, Afghanistan, but Western officials say weapons have been crossing the border from Iran and found their way into the hands of the Taliban, though they say this may be partly because the area is already full of weapons held by well-equipped drugs smuggling gangs. Shi'ite Muslim Iran is vehemently opposed to the strict Sunni views of the Taliban and almost went to war with Afghanistan when the Taliban were in power in 1998. But analysts suggest Iran could assist its sworn enemy if that meant hurting the United States during any conflict.

HOSTAGE-TAKING

Iran was blamed by the West for helping mastermind some of the kidnappings of U.S. and other foreigners during the 1975-1990 civil war in Lebanon. The Iran-Contra Affair involved selling arms to Iran, at the time fighting Iraq, in return for Tehran's assistance in releasing hostages held by Lebanese groups. In an added twist, profits from the arms sales were used to fund anti-Communist rebels, the Contras, in Nicaragua. The dealings were exposed in 1986.

(Writing by Edmund Blair; Editing by Samia Nakhoul)