"The air force has built up a solid barrier against any kind of strike, using up-to-date equipment as well as unique military tactics," Iran's Air Force chief Brigadier General Ahmad Miqani said.

The Iranian forces would remain vigilant to defend the country's airspace in case of any attack, he added.

Iran has test-fired its Shahab-3 missile that is capable of hitting targets within a range of 2,000 km, vowing that its missile capabilities are "a defensive tool against invasions."

The United States and its allies have accused Iran of trying to develop nuclear weapons under the cover of a civilian nuclear program. Iran has denied the US charges and insists that its nuclear program is for peaceful purposes only.

The United States said it focused on diplomacy to try to resolve Iran's nuclear issue, but has insisted it will take "no option off the table."

Some observers believe that it is still possible that the United States and Israel would attack Iranian targets for Tehran's suspicious nuclear programs.

In June, the New York Times reported that US military believed a major military exercise by Israel in early June was a rehearsal for a potential bombing attack on Iran's nuclear sites.

Some US officials said the Israeli exercise appeared to be an effort to develop the military's capacity to carry out long-range strikes and to demonstrate the seriousness with which Israel views Iran's nuclear program.