Washington's military commitments to Iraq and Afghanistan would hamstring an attempt to wage war on Iran, the Iranian foreign minister has said.
Mottaki said Iran would defend itself against a strike
"Our analysis is clear: [the] US is not in a position to impose another war in our region, against their taxpayers," Manouchehr Mottaki told reporters.
He warned Washington against making such a "mad decision".
Iran rejects accusations that it is seeking to build atomic weapons under the cover of a nuclear power programme.
Despite its conviction that the US would find launching another military assault extremely taxing, Iran was making preparations for such an attack, Mr Mottaki said on the fringes of a UN General Assembly session in New York.
He said information had been received which gave specific details of planned strikes.
The US says it is pursuing a diplomatic resolution but has refused to rule out a strike against Iran.