Tuesday is the target date in the nuclear talks for a preliminary agreement that would set the stage for a further round of negotiations toward a comprehensive deal by June 30.
The goal is a long-term curb on Iran's nuclear activities, with Tehran gaining relief from the burden of economic penalties imposed by the West.
Foreign ministers and other representatives from Iran and the six powers in the talks have said the negotiations have a chance of succeeding by Tuesday.
White House spokesman Josh Earnest said US negotiators were aiming for a strong deal. By accepting constraints on their atomic activities, the Iranians would "live up to their rhetoric that they are not trying to acquire a nuclear weapon," he said in Washington on ABC's "This Week."
Also Read
Israeli Prime Minister Benjamin Netanyahu renewed his vocal criticism of what he considers a looming diplomatic victory for Iran, and feared that any deal would not stop Tehran from having the ability to produce nuclear arms. He said the provisions of the deal being worked on appear to "corroborate all our concerns and then some."
Over the past weeks, Iran has moved from demanding it be allowed to keep 10,000 centrifuges enriching uranium, to agreeing to 6,000. The officials said Iran now may be ready to accept even less.
Tehran also is ready to ship out all the enriched uranium it produces to Russia, which the officials said was a change from previous demands that it be allowed to keep a small amount in stock.
One official cautioned that Iran had previously agreed to this but changed its mind.
Uranium enrichment has been the chief concern in over more than a decade of international attempts to cap Iran's nuclear programmes.