They said such action would have "disastrous consequences" for security in the Middle East and also for coalition forces in Iraq.
They said the crisis over Tehran's nuclear programme must be resolved through diplomacy, urging Washington to start direct talks with Iran.
The letter was published in Britain's Sunday Times newspaper.
It was signed by:
- Lt Gen Robert Gard, a former military assistant to the US defence secretary
- Gen Joseph Hoar, a former commander-in-chief, US Central Command
- Vice Adm Jack Shanahan, a former director of the Center for Defense Information
Incidentally, as a former CentCom commander, Hoar would have had Iran on his to-do list.
Here's the full text of the letter:
AS FORMER US military leaders, we strongly caution against the use of military force against Iran. An attack on Iran would have disastrous consequences for security in the region, coalition forces in Iraq and would further exacerbate regional and global tensions. The current crisis must be resolved through diplomacy.
A strategy of diplomatic engagement with Iran would serve the interests of the US and the UK and potentially could enhance regional and international security. The British government has a vital role to play in securing a renewed diplomatic push and making it clear that it will oppose any recourse to military force. The Bush administration should engage immediately in direct talks with the government of Iran without preconditions. There is time available to talk, we must ensure that we use it.