Washington, which says Iran seeks atomic bombs, told Tehran to halt further tests. Iran, the world's fourth largest oil producer, says its nuclear programme is only for electricity.
Iran's missile tests rattled oil markets, helping crude prices to rebound about $2 a barrel after recent falls.
Speculation that Israel could bomb Iran has mounted since a big Israeli air drill last month. U.S. leaders have not ruled out military options if diplomacy fails to end the nuclear row.
But the United States gave no hint to leaders of a group of eight rich nations meeting in Japan this week that it planned to attack Iran, Italian Prime Minister Silvio Berlusconi said.
"No mention of a military option (was made) by the United States," he said in Toyako, Japan.
Revolutionary Guards air force commander Hossein Salami said in televised comments that thousands of missiles were ready to be fired at "pre-determined targets". Missiles were shown soaring from desert launchpads, leaving long vapour trails.
"We warn the enemies who intend to threaten us with military exercises and empty psychological operations that our hand will always be on the trigger and our missiles will always be ready to launch," he said, according to ISNA news agency.
The White House told Iran to "refrain from further missile tests if they truly seek to gain the trust of the world".
U.S. Democratic presidential candidate Barack Obama called for harsher measures against Tehran after the tests. "Iran is a great threat. We have to make sure we are working with our allies to apply tightened pressure on Iran," he declared.
His Republican opponent John McCain voiced support for a U.S. missile shield as a defence against Iranian missiles.
The tests "demonstrate the need for effective missile defence now and in the future, and this includes missile defence in Europe as is planned with the Czech Republic and Poland," McCain said in a statement.
MISSILE SHIELD
U.S. Secretary of State Condoleezza Rice suggested the tests justified plans for such a system, which Russia firmly opposes.
"Those who say that there is no Iranian threat against which to be building missile defences perhaps ought to talk to the Iranians about ... the range of the missiles that they test fired," Rice said in Bulgaria.
"These are very dangerous missiles -- that's why the international community and not just Israel has an interest in blocking this escalation in a definitive way," Italian Foreign Minister Franco Frattini said in Ramallah, in the West Bank.
Iran's State Press TV said the "highly advanced" missiles tested by the Guards included a "new" Shahab 3 missile, which officials have said could reach targets 2,000 km (1,250 miles) away. Iran has said Israel and U.S. bases are in its range.
Some U.S. facilities across the Gulf are little more than 200 km from Iran's coast. The United States has air and naval bases in nearby Arab states, including Qatar and Bahrain.
Iran has said U.S. forces are vulnerable because of their presence in two of its neighbours, Iraq and Afghanistan.
Israel, believed to be the Middle East's only nuclear-armed power, has vowed to prevent Iran from acquiring an atomic bomb."Israel does not threaten Iran, but the Iranian nuclear programme, combined with their aggressive ballistic missile programme, is a matter of grave concern," Mark Regev, spokesman for Israeli Prime Minister Ehud Olmert, said after the tests.
World powers have offered Iran incentives if it suspends uranium enrichment. Tehran has rejected the demand, but Fars news agency quoted an Iranian official as saying chief nuclear negotiator Saeed Jalili would meet European Union foreign policy chief Javier Solana within days to discuss the incentives offer.
Iran has threatened to close the Strait of Hormuz, conduit for about 40 percent of globally traded oil, if it is attacked. The U.S. military says it will prevent any such action.The war of words heightens risks that a misunderstanding or a minor clash in the Gulf, for instance, could get out of hand.Tehran and Washington have not had diplomatic ties for almost 30 years and have few avenues for direct communications.
An aide to Iran's Supreme Leader was quoted as saying on Tuesday that his country would hit Tel Aviv, U.S. shipping in the Gulf and U.S. interests in reply to any military strike.
Analysts say Iran's military technology often involves improving weaponry originating in China and North Korea.
"They are some way away yet from threatening Israel or U.S. bases," said London-based independent military analyst Paul Beaver, adding guidance systems over longer ranges needed work. But he said the missile programme was still "pretty advanced." (Additional reporting by Hossein Jaseb, and Paolo Biondi in Tokayo, Japan; writing by Fredrik Dahl and Edmund Blair; editing by Alistair Lyon and Charles Dick)
