Iran test-fired more long-range missiles this morning, shrugging off international concern over yesterday's launches as the US sharpened its rhetoric against Tehran.

Weapons with "special capabilities" were launched from navy ships in the Gulf, state television reported, along with torpedoes and surface-to-surface missiles.

The launches will be taken as a sign of defiance hours after the US Secretary of State, Condoleezza Rice, made clear that America would defend its "allies," meaning Israel, if Iran threatened them.

"We are sending a message to Iran that we will defend American interests and the interests of our allies," she said, during a visit to Georgia.

"We take very seriously the obligation to defend our allies and we intend to do that."

She said the US had "enhanced its security capacity" in the Gulf and was working with its allies to make sure "they are capable of defending themselves."

The comments struck a firmer tone than her reaction to yesterday's tests, which she described only as "evidence that the missile threat is not an imaginary one", in comments interpreted as a dig at Russia, which has opposed a US missile defence shield in Europe.

Dr Rice has been in eastern Europe drumming up support for the scheme, and earlier this week signed a deal with the Czech government to site radar interceptors in the country, provoking a belligerent response from Moscow.

Few details were given about the fresh Iranian tests, although state media said they included the firing of the Hoot (Whale) torpedo, unveiled in 2006, which Iran describes as a super-fast weapon capable of hitting enemy submarines.

Another state channel quoted the chief of the Republican Guard joint staff, General Mohammad Hejazi, describing the launches as a "defensive measure against invasions". In recent days, Iranian officials have issued conflicting statements about the country's militiary intentions.

Earlier this week an aide to the supreme leader vowed to "set fire" to Israel and US ships if Iran was attacked, while President Mahmoud Ahmedinejad dismissed the possibility of an Israeli pre-emptive strike as a "funny joke".

Israel today put on display an advanced surveillance plane of type that would likely play a central role in any strike on Iran. The Israeli Air Force has taken delivery of three modified Gulfstream business jet, packed with sophisticated intelligence-gathering and communication equipment, and showed off an example today to journalists at Ben-Gurion airport in Tel Aviv. An air force spokeman denied that this was a specific reaction to Iran's war games, saying that the timing was "completely coincidental".

The Pentagon, meanwhile, was reported to be analysing yesterday's launches closely to determine the distance and accuracy of the missiles. Iranian officials say that the Shahab-3 fired yesterday has a range of 1,250 miles (2,000km), putting Israel, Turkey, Saudi Arabia, Afghanistan and Pakistan within range.

Robert Gates, the US Secretary of Defense, said it was not yet known whether the tests revealed military capabilities Iran had not been known to possess. However, he commented: "I think this certainly addresses the doubts raised by the Russians that the Iranians won't have a longer-range ballistic missile for 10 years to 20 years. The fact is they've just tested a missile that has a pretty extended range."

With only six months of the Bush presidency left to run, the US is keen to boost diplomatic efforts to persuade Iran to abandon its nuclear ambitions, while using a refusal to rule out military options as a spur to that end.

Dr Rice's Undersecretary of State, William Burns, told the Senate Foreign Relations Committee in Washington yesterday that the US was considering delaying a drive for more UN sanctions on Iran in exchange for a freeze on new Iranian economic activity.

Such a "freeze-for-freeze" proposal would represent a softening of the US line that Iran must suspend uranian enrichment before any negotiations can take place. Mr Burns described the idea as "further evidence of our seriousness about reaching a diplomatic solution of this very, very, serious problem".

Times Recommends

• Both sides blame US for worsening relations
• Stieg Larsson: losing the plot over his cash
• Odd creature paralysed by incompatible parts