Sen. Bob Corker, R-Tenn., the top Republican on the Foreign Relations Committee, said Congress will not be able to pass a new round of sanctions before talks this weekend between the international community and Iran on Tehran's nuclear program.

Corker, emerging from a meeting with President Obama and a bipartisan group of senators at the White House on Tuesday, expressed reservations about the direction the Obama administration was taking in the talks but said he needed time to evaluate his next step.

“There was a strong meeting and a lot of questions were asked and a lot questions were answered,” he said. “You had some folks in the room that were satisfied, you had some folks in the room who were unsatisfied.”

Corker also expressed concerns that the U.S. is “giving away leverage” in pursuing a partial deal.

“I think all of us are concerned because we know who we're dealing with — we watched this same activity from North Korea,” he said. “I think what the concern is — whatever you do on an interim basis becomes the new norm.”

The U.S. is negotiating a deal with Iran that would lead to temporary, partial sanctions relief in exchange for Tehran freezing elements of its nuclear program. But that approach, which eases some sanctions, has raised concerns on Capitol Hill and among U.S. allies who fear that the administration is weakening pressure on Iran.

Some lawmakers called for an additional round of sanctions to further tighten the screws on Iran to abandon its nuclear ambitions.

Senate Majority Leader Harry Reid, D-Nev., though, is refusing to allow any amendments on the defense authorization bill, the only vehicle that is moving in the Senate before Congress's Thanksgiving holiday next week.

During Obama's meeting with senators Tuesday, the president asked lawmakers to delay any attempt to pass a new round of sanctions to give time for the fragile negotiations to produce a preliminary deal.

The president later Tuesday publicly defended the Iran talks, saying the deal both sides are considering would not impact the most severe sanctions.

“Oil production and oil sales out of Iran have dropped by more than half since these sanctions have been put in place,” Obama said at the Wall Street Journal's annual CEO Council. “All of those sanctions and the architecture for them don't go anywhere… the oil and banking sanctions stay in place.”

Obama was responding to criticism from Israeli Prime Minister Benjamin Netanyahu, who said any attempt to provide any economic relief to Iran in an interim deal could result in the entire international sanctions regime crumbling.

Netanyahu, along with Corker and other key lawmakers, have also said they are worried that any partial or interim six-month deal that did not force Iran to make full concessions would undermine any leverage the sanctions have produced.

Obama described the six-month deal as a way to “buy time” to see just how serious Iran is about halting the development of its nuclear program.

“What we're suggesting, is, 'Look, let's test the proposition that over the next six months we can resolve this in a diplomatic fashion while maintaining the sanctions architecture,'” he said. “We're purchasing ourselves some time to see how serious the Iranians are in returning to the international community and taking this yoke of sanctions off their economy.”

On Capitol Hill, some lawmakers expressed a willingness to take a wait-and-see approach on another round of sanctions until the outcome of negotiations was more clear.

"It would blow things apart. There's no doubt in my mind it would splinter [negotiations]... It would not only split it apart but do it in a way that would make it very difficult to come back together," said Sen. Dianne Feinstein, chairwoman of the Senate Intelligence Committee. "If you want a war, that's the thing to do."

Sen. John McCain, R-Ariz., said he was receptive to the president's concerns and open to delaying immediate action on sanctions.

"You always have to listen to the president of the United States when he asks you to do something," he said. "Of course we want to seriously consider doing what he wanted, especially in the midst of some serious negotiations."

Congressional correspondent Tim Mak contributed to this report.