US to walk away from Iran nuclear talks if 'significant gaps' not closed ahead of 'looming deadline'

As the deadline to reach an agreement on Iran's nuclear programme looms large, United States Secretary of State John Kerry has said that "significant gaps" remained and cautioned that the U.S. was ready to walk away from the negotiations if Tehran down not demonstrate its willingness to curb its nuclear ambitions.

Kerry made the statement after Iranian Atomic Energy chief Ali Akbar Salehi and U.S. Energy Secretary Ernest Moniz added their muscle to the talks for the first time to help resolve key sticking points in the way of a nuclear deal, reported The Washington Times.

Warning against "undue optimism," Kerry said that Salehi's and Moniz's presence was no "indication whatsoever that something is about to be decided."

He warned that there was no doubt that President Barack Obama was "serious" and prepared to halt the dialogue process if he felt that "they're not being met with the kind of productive decision-making necessary to prove that a program is in fact peaceful."

World powers and Iran had set an end of March deadline to reach a framework agreement, with four months to work out the technical details of the deal. The deadline to secure a deal has been postponed twice previously. Obama had earlier remarked that a further extension would make little sense without a basis for continuing discussions.

The P5+1 nations, including, the U.S., the United Kingdom, France, Germany, Russia and China, accuse Iran of building nuclear weapons under the pretense of developing its nuclear capabilities for civilian purposes. They want Tehran to curb its nuclear ambitions in return for the lifting of United Nations sanctions.