"I want to reiterate that these talks can only make progress if the Iranians come to the table determined to make and discuss real offers and engage in a real dialogue," Kerry said in a press conference alongside visiting UN Secretary-General Ban Ki-moon before their meeting.

　　"Countries that have peaceful programs do not have problems proving to people that they are peaceful," the newly-installed U.S. chief diplomat stressed. "So we are not going to get trapped into a delay-after-delay process here."

　　As Iran agreed to start fresh talks with the so-called P5+1 group -- Britain, China, France, Russia, the United States and Germany -- on Feb. 26 in Kazakhstan, the Obama administration has time and again urged its arch-rival to engage in "substantive" negotiations over its disputed nuclear program in return for eased sanctions.

　　"I think it is incumbent on the Iranians to prove that they are prepared to meet our willingness, President Obama's willingness, again and again stated by the President, to be open to a diplomatic resolution here," Kerry noted.

　　Iran and the West are locked in a bitter dispute over the former's nuclear activities, with the latter accusing Tehran of developing nuclear weapon under a civilian cover, a charge Iran has consistently denied.

　　Iran has insisted that its rights to peaceful nuclear activities, and above all the right to uranium enrichment, be recognized by the IAEA and world powers.