"We've got a leader in Iran who has announced that he wants to destroy Israel," Bush said at a White House press conference after Russia cautioned against military action against Tehran's suspected atomic program.
"So I've told people that, if you're interested in avoiding World War III, it seems like you ought to be interested in preventing them from having the knowledge necessary to make a nuclear weapon," said Bush.
'US will continue to work with Russia'
Bush added he was not worried by growing Russian-Iran ties and will continue to work with Russian President Vladimir Putin on ways to defuse Iran's nuclear program.
"He (Putin) recognizes it's not in the world's interests for Iran to have the capacity to make a nuclear weapon, and they have been very supportive in the United Nations," Bush said.
The US president's remarks came as Putin and Iranian President Mahmoud Ahmadinejad wrap up a landmark summit in Iran, at which the Russian leader put forward a proposal to break the deadlock over Iran's nuclear program.
No further details were given on Putin's proposal, which was made during his talks on Tuesday with Iran's supreme leader Ayatollah Ali Khamenei.
"I'm looking forward to getting President Putin's read-out from the meeting," Bush said.
"The thing I'm interested in is whether or not he continues to harbor the same concerns that I do," Bush added.
"I will continue to work with Russia as well as other nations to keep a focused effort on sending Iran a message that you will remain isolated if you continue your nuclear weapons ambitions," the US president said.