US national security adviser, Susan Rice, told CNN on Tuesday that Washington was considering unfreezing about $10 billion to relax sanctions against Iran. “We're talking about a modest amount of money,” Rice said.

In a closed-door meeting at the White House, the US president has once again told senators that the next round of negotiations in Geneva on Wednesday were the best chance of “stopping the advance” of Iran’s nuclear program “for the first time in nearly a decade,” according to press secretary Jay Carney.

“We have the opportunity to halt the progress of the Iranian program and roll it back in key respects, while testing whether a comprehensive resolution can be achieved,” the White House said in a statement.

Obama also told the politicians to hold off on new sanctions and rejected reports that Iran would receive up to $50 billion in sanctions relief.

In exchange for halting Iran’s nuclear activity, Carney said, US was willing to offer “limited, temporary and reversible” relief from some sanctions under a P5+1 proposal.

“Part of the reason I have confidence that the sanctions don't fall apart is because we're not doing anything around the most powerful sanctions,” Obama said later at an event sponsored by The Wall Street Journal.

Yet the president warned about being over optimistic, “I don't know if we will be able to able to close a deal this week or next week.”

A bipartisan group of six senators has written to Secretary of State John Kerry warning against a possible deal with Iran.

Iran has categorically rejected the allegation, arguing that as a signatory to the Non-Proliferation Treaty (NPT) and a member of the International Atomic Energy Agency (IAEA), it has the right to use nuclear technology for peaceful purposes.

NTJ/BA