Bush also acknowledged that mistaken intelligence on Saddam Hussein's weapons programs in Iraq makes it more difficult to persuade the public that Iran's nuclear program poses a threat.
Bush's remarks, at a press conference in Washington, came two days before Britain, France, and Germany are due to have fresh talks with Iran on its controversial nuclear program.
A spokeswoman for EU foreign policy chief Javier Solana said today the talks would take place "discreetly" in Vienna.
Gholam Reza Aghazadeh, head of Iran's Atomic Energy Organization, said his country will bring new proposals to the talks. But he said Iran's right to develop a nuclear power program must be recognized.