Iran expressed dissatisfaction with proposals made by the six world powers and cast doubt on the prospect of a new round of talks unless there were an agreement to hold off on sanctions that are to take effect in July, The New York Times reported.
Saeed Jalili, Iran's lead negotiator, met twice Thursday with the European Union's top foreign policy official, Catherine Ashton, who is leading the six-power negotiation team, and Iranian media reported Ashton had not presented anything new.
Iranian media said the republic had presented a five-point proposal with nuclear and non-nuclear elements.
As Day 2 of negotiations began, the state-run Press TV said sources close to Iran negotiators said prospects for talks were "vague and under question" if the powers rejected the Iranian plan.
Iran had balked at the six global powers' refusal to offer sanctions relief in negotiations over its disputed nuclear program as the second day of negotiations began in Baghdad Thursday.
Iran's official Islamic Republic News Agency said the proposal package from the United States, France, Britain, Russia, China and Germany would have to be significantly revised for the talks to be productive.
The five permanent Security Council members and Germany, known as the P5-plus-1, rejected Iranian calls Wednesday for an immediate easing of economic sanctions -- imposed on Tehran for disregarding U.N. Security Council resolutions demanding Iran end all nuclear enrichment, senior Western officials involved in the talks said.
The six powers said harsher U.S. and European Union sanctions on oil exports and banking transactions would go into effect in July, as planned.
IRNA said late Wednesday the West was expecting disproportional concessions while offering few incentives.
The United States has said Iran must first take significant steps toward addressing Western, Israeli and U.N. concerns Iran seeks nuclear weapons before Washington loosens sanctions. Iran insists its nuclear program is purely civilian.
Despite the deadlock, U.S. and European officials said they remained committed to finding a solution.
"I would have expected nothing more than Iran to say that this [offer] was unbalanced. This is a negotiation," a senior U.S. official involved in the talks was quoted by The Wall Street Journal as saying.
The negotiations are a process, said Michael Mann, spokesman for European Union foreign policy chief Catherine Ashton, who led the P5-plus-1 side in the talks with Jalili.
"These things can't be resolved overnight," but if the talks go well here, "we are going to make solid progress," he said.
The six powers told Iran they wanted it to stop enriching uranium to 20 percent purity, officials said.
The level of enrichment is far higher than needed for routine energy-producing reactors and a short technical step away from bomb grade.
The powers want Iran to surrender its existing stockpile of 20 percent uranium, which the powers would later return as processed fuel for medical reactors.
The P5-plus-1 said Iran would need at some point to dismantle a once-secret enrichment plant, carved deep into a mountain 20 miles north of the holy city of Qom, where Iran is allegedly producing the highly enriched uranium, The New York Times reported.
In return for early Iranian steps to stop enriching uranium to 20 percent, the six offered to ease sanctions barring exports of U.S.-made spare parts for civilian aircraft, officials said. They also offered to help with nuclear development and safety at civilian nuclear power installations and perhaps a pledge that Iran has a right to a peaceful nuclear program, as long as it erases doubts about its intentions, people briefed on the talks told several news organizations.
Iran's counteroffer included what it called a comprehensive road map of how it believed the negotiations should progress, IRNA reported.
The Iranian proposals included details on what compromises Iran would make and what it expected its international counterparts to offer, as well as propositions about "other international issues," IRNA said.
"In Iran's package, the give and take is balanced," the government news agency said.