US President George W Bush has said that diplomacy is the "number one option" to resolve the dispute with Iran over its nuclear activities.
Mr Bush said the goal was to stop Iran getting nuclear weapons
He was speaking hours after foreign ministers of major powers meeting in New York failed to agree on how to tackle the problem.
Meanwhile the White House said it would not reply in writing to a letter sent by Iran's president to Mr Bush.
The surprise letter by Mahmoud Ahmadinejad criticises US policy.
He attacks the US invasion of Iraq and urges Mr Bush to return to religious principles.
US Secretary of State Condoleezza Rice dismissed the letter as "offering nothing new".
"This letter is not the place that one would find an opening to engage on the nuclear issue or anything of the sort," Ms Rice told the Associated Press news agency.
Mr Bush said the common goal of the international community was to make sure Iran did not acquire a nuclear weapon.
"The first choice and a choice that I think will work with the Iranians is diplomacy, and I believe we can accomplish this through diplomacy," he said.
Earlier Ms Rice held an inconclusive three-hour meeting with her UN Security Council counterparts and the German foreign minister on what action to take over Iran.
BBC diplomatic correspondent James Robbins says that far from drawing the key powers at the UN towards agreement on the issue, the meeting seems to have exposed the scale of division.
The UK, France and Germany will now spend three days discussing a package which will give Iran benefits if it co-operates as well as sanctions if it does not.
Correspondents say Russia and China have been calling for carrots as well as sticks for Iran - so diplomats hope if this package can be agreed then a resolution on Iran could be tied up.
Washington has pushed for any resolution to be adopted under the terms of Chapter Seven of the UN Charter.
These are binding on all UN members, but do not automatically lead to sanctions or military action. Further decisions would be needed for such measures.
But China and Russia have resisted such a move, fearing it could lead to a new war.
The letter - thought to be the first from an Iranian president to a US leader since Iran's 1979 revolution - sparked intense interest, coming at a time of tension between Washington and Tehran.
In the 18-page document, Mr Ahmadinejad spoke of the invasion of Iraq, and a range of other issues.
"Lies were told in the Iraqi matter," it said. "What was the result? I have no doubt that telling lies is reprehensible in any culture."
The president also questioned the creation of Israel, asking "how can this phenomenon be rationalised or explained?".
In an apparent allusion to Iran's nuclear programme, Mr Ahmadinejad asks: "Is not scientific R&D [research and development] one of the basic rights of nations?"
White House officials said there would not be a written response to President Ahmadinejad.
"We've already given our response," National Security Council spokesman Frederick Jones told the AFP news agency, referring to the swift dismissal by US officials of the letter as a ploy which contributed nothing towards helping resolve the stand-off over Iran's nuclear programme.