"Obama is preparing for a (military) offensive on Iran with the help of his ally, the Israeli regime," IRNA quoted Mohamad as writing on his weblog.
Mahathir said that President Barack Obama, who had received the Nobel Peace Prize, did not fulfill his promises regarding withdrawal of US troops from Iraq and Afghanistan as well as a pledge to close the Guantanamo prison.
Obama "has not even fulfilled one word of his promises," he said.
Mahathir went on to say that the US is expected to launch the war on Iran on the pretext that the Islamic Republic was seeking to build a nuclear bomb.
He said that the US will introduce "forged evidences" showing Iran aims to "start a nuclear war against the world."
Tel Aviv and Washington have never ruled out the possibility of a military strike against Iran, which is accused by the US, Israel and some European countries of aiming to develop nuclear weapons under the cover of its civilian nuclear program.
While categorically denying the allegations, Iran says it has the capability to ward off any attack on the country and has stressed that an Israeli or US strike would meet a 'decisive' response from Tehran.
Iran says its nuclear program is meant to meet the civilian needs of its people and is being pursued within the framework of international atomic agency regulations.
Mahathir also referred to Iraq that came under the occupation of the US and its allies on the pretext that the country has weapons of mass destruction — a claim which proved to be untrue.
He questioned "whether we could believe that the war against Iran will be because of its potential nuclear strike against the world?"