Bernard Kouchner, France's foreign minister, created a stir last weekend when he raised the spectre of war, though he later said the comments were meant as a warning against military action and not to incite it.
The US is among a number of countries who suspect Iran is trying to develop nuclear weapons.
Iran insists it wants nuclear technology strictly for electricity generation.
Bush, who will attend the UN General Assembly in New York next week, said he would emphasise a move towards economic sanctions against Iran in his talks with members of the UN Security Council.
He said: "We are working with allies and friends to send a consistent message to the Iranians that there is a better way forward for them than isolation - financial isolation and, or economic sanctions.
"I believe it's imperative that we continue to work in a multilateral fashion to send that message. And one place to do so is at the United Nations."
However, Bush could face resistance to a push for any new sanctions.
The UN has already adopted two sets of sanctions against Iran, though they were watered down at Russia's insistence.
This week, Vitaly Churkin, Russia's ambassador to the UN, questioned whether new sanctions would solve the problem and if quick action was needed.
Churkin said: "The big question is whether we should rush to adopt new resolutions on sanctions."
Bush also voiced support for a decision by New York City officials to reject Mahmoud Ahmadinejad's, the Iranian president, request to visit the World Trade Center site of the September 11 attacks.
He said: "I would understand why they would not want somebody that's running a country that's a state sponsor of terrorism down there at the site."