"Iran must make the decisions necessary to resolve several remaining issues," the White House said, in a statement released after the two leaders spoke by telephone.
They pressed for a "long term comprehensive deal."
Senior officials from six countries, including Germany and the United States, are holding talks with Iran ahead of an end of March 31 deadline for an interim deal.
A number of major issues appear yet to be resolved, including the phasing out of sanctions and inspections of Iranian nuclear facilities.