President Bush has demanded that Iran give up nuclear weapons ambitions "for the sake of world peace".
Mr Bush made his comments during a meeting with German Chancellor Angela Merkel.
Both leaders said it was important for the international community to stay united in the drive to stop Iran from developing a nuclear weapon.
"The Iranians must understand that we won't fold, that our partnership is strong, that for the sake of world peace, they should abandon their nuclear weapons ambitions," Mr Bush said.
Ms Merkel, who came to Washington intent on mapping out a strategy for confronting Iran that will not splinter the West as Iraq did three years ago, said she and Mr Bush saw good chances for bringing about a diplomatic solution.
Although Mr Bush in the past has not ruled out military options, he stressed diplomacy and said last week that diplomatic options were just beginning on Iran.
Iran says its nuclear programme is for peaceful power generation and will not give it up.
Mr Bush said it was a "good starting point" that Russia agreed on the ultimate goal that Iran not have a nuclear weapon.
Mr Bush and Ms Merkel's meeting came as Britain, France, and the United States introduced a UN Security Council resolution demanding Iran suspend uranium enrichment that the West suspects is part of a secret nuclear weapons programme.