A surprise letter to the US president from Iranian leader Mahmoud Ahmadinejad will not solve the growing nuclear dispute, US officials have said.
It was not confirmed that Mr Bush had read Mr Ahmadinejad's letter
Secretary of State Condoleezza Rice dismissed hopes of a diplomatic breakthrough, telling the Associated Press: "This letter is not it."
The letter is thought to be the first from an Iranian president to a US leader since Iran's 1979 revolution.
It came hours before a meeting of UN Security Council members in New York.
Foreign ministers of the council members plus Germany were due to meet on Monday night to discuss how to proceed with Iran.
Mr Ahmadinejad dispatched the letter via the Swiss embassy in Tehran.
In it, he proposed "new solutions for getting out of international problems and the current fragile situation of the world", Iranian officials said on Monday.
But the White House joined Ms Rice in quickly denouncing the letter.
"It doesn't appear to do anything to address the concerns of the international community," White House spokesman Scott McClellan told reporters.
There has been no word on whether the letter mentioned the nuclear dispute, currently one of the major issues between Iran and the US.
Interviewed by AP, Ms Rice said: "There's nothing in here that would suggest that we're on any different course than we were before we got the letter."
Mr McClellan would also not confirm whether Mr Bush had personally read the letter, saying only: "I would just leave it at what I said: We've received it."
This development comes a day after Iran's parliament threatened to pull out of the nuclear Non-Proliferation Treaty if Western pressure over its programme increases.
A withdrawal would mean the country's programme could no longer be inspected by the UN nuclear watchdog, the International Atomic Energy Agency.
The letter's contents have not been revealed, but it was said to run to 17 or 18 pages of history, philosophy and religion.
Iranian Foreign Minister Manuchehr Mottaki said Tehran would not prejudge the US reaction to the letter.
"We hope that this letter would leave its impact with the same intention, view and expediency that it has been written," he told Iranian TV.
The US has accused Iran of seeking to develop nuclear weapons - a charge Iran strongly denies.
Last week, the US and other states tabled a draft resolution at the UN Security Council calling on Iran to suspend uranium enrichment or face "further action".
The BBC's Frances Harrison in Tehran says whatever is in the letter, it is significant because it is the first such high-level communication between Iran and America for almost three decades.
As such it is a bold step by Mr Ahmadinejad, and the timing is key - just as the West is trying to persuade Russia and China to back tough action against Iran, she says.
Mr Ahmadinejad is reinforcing the point that he is willing to negotiate with anyone, including the US president, to avoid conflict over the nuclear issue, our correspondent adds.
The US and Iran have not had diplomatic relations since Washington severed ties with Tehran after Iranian students occupied the US embassy there and took 52 Americans hostage in 1980.