The comments by Gen. Amir Ali Hajizadeh, who heads the Guard's aerospace division, came amid tension over Iran's nuclear program and Israel's suggestion that it might unilaterally strike Iranian nuclear facilities to scuttle what the United States and its allies believe are efforts to build a bomb. Tehran says its nuclear program is for peaceful purposes.

Hajizadeh said no Israeli attack can happen without the support of its most important ally, the United States, making all U.S. military bases a legitimate target.

"For this reason, we will enter a confrontation with both parties and will definitely be at war with American bases should a war break out," Hajizadeh said in remarks that were posted on the website of Iran's state Al-Alam TV. U.S. facilities in Bahrain, Qatar and Afghanistan would be targeted, he said.

"There will be no neutral country in the region," Hajizadeh said. "To us, these bases are equal to U.S. soil."

The U.S. Fifth fleet is based in Bahrain and the U.S. has a heavy military presence in Afghanistan.

The Iranian warning appears an attempt to reinforce the potential wider consequences of an attack by Israel. The message is not only intended for Washington, but to its Gulf Arab allies that are fearful of a regional conflict that could disrupt oil shipment and cripple business hubs in places such as Dubai and Qatar's capital Doha.