Iranian lawmaker Mohammad Karamirad on Wednesday said Iran will formally respond on Thursday to a UN-drafted plan to ship much of its uranium abroad for enrichment.
Another lawmaker, Alaeddin Boroujerdi, said Iran's top security body will make a final decision on the proposal later Wednesday.
Iran's state media have said the country would agree to the plan's general framework but would demand important changes.
According to the UN-drafted deal, Iran would ship much of its uranium to Russia and France for further enrichment, setting back the nuclear program and the time-frame in which Iran could reach "breakout" capacity.
Also Wednesday, opposition leader Tzipi Livni told Russian Foreign Minister Sergei Lavrov that the world should learn from Iran's past conduct and "understand that it doesn't act with transparency, honesty or openness toward the international community."
She criticized the draft agreement, saying that the deal leaves Iran its enrichment capability, and "instead of solving the problem, only delays it," adding that "at best, we'll be at the same point we are now in a year."
She said the world must "put a stop" to Iran's enrichment capability.
"Dialogue with Iran cannot go on forever, and today, more than ever, it's clear that Iran's aim is to attain nuclear weapons, and that to accomplish this goal, it will use various ways of trying to avoid arrangements that don't enable it to continue its nuclear program." Livni continued. "Only by leaving all options on the table can we ensure the effectiveness of dialogue."
Earlier Wednesday, Livni warned that "Iran is toying with the world," and said the current proposed deal between the West and Teheran might not be sufficient to ensure the Islamic republic does not achieve military nuclear capability.
"Iran is toying with the world. The deal doesn't solve a major issue - the complete halt of uranium enrichment. There's a clear international consensus that a nuclear Iran is unacceptable," Livni said in a statement during her a one-day visit to Moscow.
Livni went on to warn that the demands set by the international community must not be eroded. "We are now in the critical point in time - the offer is on the table and the powers have announced they accept the idea, but it is important to prevent erosion," she said.
"The current deal provides a partial solution, as it doesn't prevent Iran from enriching uranium during the negotiations. Obviously, this is not only an Israeli problem, there are Arab and Muslim states that would not accept a nuclear Iran."
Meanwhile in New York, US National Security Adviser James Jones on Tuesday said Washington is prepared to respond if Teheran does not abide by its nuclear commitments.
Speaking at a J Street convention, Jones emphasized that halting Iran's enrichment of uranium was the goal of the deal endorsed by Washington, and that "nothing is off the table" when it comes to dealing with the issue.
"We will see if engagement is able to produce the concrete results we need, and we'll be prepared if it does not," Jones was quoted by AFP as saying.
Also on Tuesday, French Foreign Minister Bernard Kouchner said Iran must make haste in its negotiations with the group of international powers - including the United States, Russia and France.
"It cannot take forever. We wait for answers," he said.
Hilary Leila Krieger and AP contributed to this report