UNITED NATIONS — Iranian President Mahmoud Ahmadinejad used his first speech before the United Nations to blast the U.S. and urged the body to prevent members from taking "pre-emptive" action, even as France echoed a U.S. threat to Iran over its nuclear development.

Ahmadinejad labeled the doctrine of pre-emption — the Bush-administration policy that calls for striking an adversary before it gains the capability to launch its own attack — as a "blatant contradiction to the very foundations of the United Nations and the letter and spirit of its charter."

Soon after Ahmadinejad got up to speak, two U.S. diplomats left the General Assembly hall, leaving two U.S. note-takers behind. The U.S. Mission denied any symbolism in the decision.

Tensions between the two foes have escalated over Iran's pursuit of a nuclear program that the Bush administration maintains is designed to manufacture weapons.

Bush discussed the Iranian nuclear issue with Chinese President Hu Jintao yesterday and with British Prime Minister Tony Blair and Russian President Vladimir Putin today.

French Prime Minister Dominique de Villepin threatened Iran yesterday with referral to the U.N. Security Council if it fails to suspend the nuclear program.

Outside the U.N., hundreds of people protested Ahmadinejad's visit. Some carried posters that described him as "Terrorist Hostage Taker Ahmadinejad." Compiled from Reuters, Bloomberg News and the Los Angeles Times