After months of intense negotiations, the five permanent members of the Security Council plus Germany were nearing agreement on the text of a resolution, said Undersecretary of State Nicholas Burns.
"There will be sanctions passed against Iran in the next several days at the United Nations," Burns said on CNN after President George W. Bush signed a controversial civilian nuclear deal with India, which is already a nuclear weapons power.
The United States has been leading efforts to impose sanctions against Iran over its refusal to comply with an earlier UN resolution demanding that it stop reprocessing and enriching uranium -- activity that could provide material to produce nuclear weapons.
But drawn-out negotiations with the four other veto-wielding Security Council members -- Britain, China, France and Russia -- along with Germany have so far failed to yield agreement on the exact terms of a sanctions resolution.
Russia, which has close energy and economic ties with Iran, objected to an initial draft resolution as too harsh.
But over the weekend Russian Foreign Minister Sergei Lavrov said a consensus was forming around a revised draft presented by France and Britain earlier this month.
"I hope that it is entirely realistic to come to a consensus in the days remaining before the New Year if our partners take a realistic approach and do not insist on certain positions which we are convinced have nothing to do with the task before us," Lavrov was quoted by Russian media as saying.