The BBC said government ministers are trying to determine if any involvement by Britain in such a conflict would be legal.
While ministers say they're hopeful diplomacy could head off any conflict, they are looking at what might happen if Israel carried out its threat to launch a military strike on Iran's nuclear facilities.
Options could range from diplomatic support for Israel up to actual involvement of the Royal Navy, the BBC said Wednesday.
Shadow Foreign Secretary Douglas Alexander says he is opposed to any public saber rattling "about what could happen if diplomatic said efforts fail."
"The government should be focused on ensuring a successful outcome to the talks now under way," Alexander was quoted as saying.