Lew was interrupted several times by heckling from the audience at an annual New York conference sponsored by The Jerusalem Post as he laid out the US administration's position on the nuclear negotiations.

"A diplomatic solution is the best, most enduring path to achieve our goal of keeping Iran from obtaining a nuclear weapon," he said.

Israel's Prime Minister Benjamin Netanyahu has emerged as the most vocal opponent of an agreement, warning against a "bad deal."

Iranian Foreign Minister Mohammad Javad Zarif complained about the difficulty of drafting a final deal between Tehran and the world powers, and called on the other side to harness their excessive demands and respect the Lausanne understanding if they really want a deal with Iran.

"The western countries should adopt a realistic and pragmatic view to make a comprehensive agreement possible," Zarif said in Moscow on Friday morning before leaving the Russian capital for Tehran.

He reiterated that if the other side shows respect for what was agreed in Lausanne, Switzerland, and attempts to write the text of the final agreement on the basis of mutual respect, then "we can strike a final deal" by the July 1 deadline.

The Iranian foreign minister, meantime, warned that if the western countries insist on their excessive demands in the negotiations, then the situation will grow difficult.

Zarif expressed the hope that Tehran and the World powers would reach an agreement before the deadline.