New sanctions if no progress on Iran: Bush

British Prime Minister Tony Blair (L) listens as U.S. President George W. Bush addresses a joint news conference in the Rose Garden of the White House in Washington May 17, 2007.

WASHINGTON (Reuters) - President George W. Bush said on Thursday it was important for the international community to "speak with one voice" against Iran's nuclear program and warned of new sanctions if there was no progress.

"We fully recognize that the Iranians must not have a nuclear weapon," Bush said at a news conference with British Prime Minister Tony Blair.

"If we're unable to make progress with the Iranians, we want to work together to implement new sanctions through the United Nations, to continue to make it clear that Iran with a nuclear weapon is not in the interest of peace in the world," Bush said.

Iran has installed 1,600 centrifuges used for enriching uranium and is pressing ahead with more as part of its nuclear program, according to a senior Iranian official quoted by Iran's Mehr News Agency.

The U.N. Security Council has imposed two rounds of sanctions on Iran since December, but Iran has resisted demands to halt its nuclear activity.

Western countries suspect Iran of seeking to produce nuclear weapons, which Tehran denies, saying its program is for civilian purposes.