US admiral Mullen

America's top military officer has said opening up a third front in the Middle East through a strike on Iran would be "extremely stressful" for US forces.

Adm Mike Mullen, chairman of the Joint Chiefs of Staff, was commenting on the likelihood of US or Israeli military action over Iran's nuclear programme.

Tensions have risen amid reports Israel may be planning a possible strike against Iran's nuclear facilities.

Iran denies its nuclear programme is anything other than peaceful.