The US is hoping to persuade the other four permanent members of the UN Security Council and Germany of the need for more sanctions against Iran.
Iran's nuclear programme remained secret for years
Washington wants a third round of tougher UN sanctions over its refusal to halt uranium enrichment.
Representatives from Russia, China, France, Britain and Germany are to meet in Washington to discuss the issue.
Tehran denies the accusations of the US and its European allies that it is trying to build a nuclear weapon.
The US is hoping to use the Washington meeting to lay the groundwork for a new UN Security Council resolution in the next few weeks.
'Prepare for war'
Two rounds of UN sanctions have failed to convince the Iranians to suspend uranium enrichment, a process that could eventually enable Tehran to build nuclear weapons.
US President George W Bush said recently that he "was not going to tolerate" a nuclear-armed Iran, but said the US favoured diplomacy to resolve the issue.
And French President Nicolas Sarkozy declared on French television late on Thursday that "Iran is trying to obtain an atomic bomb".
He also called for tougher sanctions, if necessary.
His Foreign Minister, Bernard Kouchner, made waves earlier this week by saying that the world should prepare for war over Iran's nuclear programme.
But Russia and China, which both have veto power in the council, have said they oppose additional sanctions.
The International Atomic Energy Agency (IAEA) has recently reached agreement with Iran on a "work plan" to resolve outstanding questions about its nuclear activities.
This plan has especially angered the Americans, but the French, British and to an extent the German governments are far from enthusiastic either, says the BBC's diplomatic correspondent Jonathan Marcus.