World powers have failed to reach agreement on a unified strategy to deal with Iran's nuclear program.
German Foreign Minister Frank-Walter Steinmeier said there are up to six issues to be resolved on a possible United Nations Security Council resolution on Iran.
U.S. Secretary of State Condoleezza Rice and her counterparts from China, Russia, France, Britain and Germany met in New York late Monday.
A senior U.S. official says the ministers agreed that Iran must not have nuclear weapons capabilities, but could not reach an accord on how to enforce this view.
Earlier Monday, the White House received a letter from Iran's President Mahmoud Ahmadinejad -- the first by an Iranian leader to a U.S. president in more than 25 years.
Secretary of State Rice said the letter did not contain any concrete proposals on resolving the nuclear dispute.
U.S. director of national intelligence John Negroponte told reporters the timing of the letter suggests Tehran is trying to undermine efforts for a binding Security Council resolution ordering Iran to suspend all uranium enrichment.
The United States suspects Iran is trying to build a nuclear weapon. Iran insists its nuclear program is for civilian energy use.
China and Russia say they will veto sanctions or any move that threatens military force against Iran.
Information for this report is provided by AFP, AP and REUTERS.