Story highlights

Skeptics in Congress want to know the U.S. is taking a hard line and pressing for the best deal possible

International partners want to know the U.S. hasn't brought them to this point for nothing

Iran needs to know the U.S. won't concede certain points but is truly willing to walk away

Washington CNN  — 

The Iran nuclear talks are progressing. But tough issues still remain. We could reach a deal. But we also might not. About 50-50. Less than 50-50.

It’s all up in the air.

Those messages are just a slice of what top U.S. officials are saying publicly as they emerge from closed-door negotiations with their Iranian counterparts, struggling to find a way to broker a lasting deal aimed at keeping Iran from a nuclear weapon.

But there’s a method to the messaging madness as the Obama administration is looking to reassure key constituencies in the U.S. while holding together an increasingly fractious coalition of countries joining them in the negotiations and also ratcheting up pressure on Iran.

READ: Iran talks checklist: Is the U.S. negotiating a bad deal?

“All of this is inevitably to some extent posturing, but it’s also real and important in terms of setting the expectations for the negotiating parties,” as well as setting the political context at home, said Suzanne Maloney, an Iran expert at the Washington-based Brookings Institution and a former State Department Iran policy adviser.

Skeptics in Congress want to know the U.S. is taking a hard line and pressing for the best deal possible. International partners want to know the U.S. hasn’t brought them to this point for nothing. And Iran needs to know the U.S. won’t concede certain points but is truly willing to walk away.

“As I have said many times and as I discussed with President Obama last night, we are not going to sit at the negotiating table forever,” Kerry said at a press conference Thursday. But he also said the U.S. isn’t pressed by time: “We shouldn’t get up and leave simply because the clock strikes midnight.”

Bold public statements that the U.S. is prepared to leave Iran hanging at the negotiating table telegraph the message that Tehran needs to budge on certain issues or it could find itself without the much-awaited sanctions relief it has chased for years.

That’s how Sen. Chris Coons of Delaware, a key Democrat on the Foreign Relations Committee, interpreted Kerry’s words.

“My hunch is that what we’re hearing here from Secretary Kerry is a determination to send a message to the Iranian Supreme Leader: ‘The deal that is on the table is the best deal you’re going to get. You either need to accept it or we’re going to walk away,’” Coons said Thursday on CNN.

Maloney said Kerry and other officials’ statements are a clear gambit to “influence Iranian expectations and Iranian decision-making” on the inside from the outside.

“Those theatrics were necessary,” Maloney said.

But they also have another audience: restive members of Congress who fear that the repeated deadline extensions are a sign that Iran is gaining the upper hand and sticking to its demands while the U.S. caves.

By passing the July 9 date that Congress set for completing the deal and turning a copy over to Congress, the administration now faces a congressional review period of 60 days rather than just 30. That’s twice as much time for vocal opponents to tear the details of the deal apart and rally votes against the measure.

So Kerry and President Barack Obama have doubled down in recent weeks on their insistence that the U.S. is willing to walk away from talks altogether if Iran won’t relent on the final, crucial sticking points.

“I will walk away from the negotiations if, in fact it’s a bad deal,” Obama said last week from the White House.

“If the tough decisions don’t get made, we are absolutely prepared to call an end to this process,” Kerry stressed on Thursday.

That’s giving some in Congress hope that the Obama administration is sticking to its guns. But it’s not clear whether the more hardened skeptics are buying the administration’s insistence that it is not flinching on key points, Maloney said.

“There’s still frustration and an overwhelming skepticism toward the administration and its ability to hold a hard line with respect to Iran,” she said.

The talking point of walking away from a deal also helps reinforce the administration’s arguments that it has worked tirelessly to obtain a good deal and that it therefore got the best one possible – should a deal be reached. And if there is no deal, the messaging will help to lower expectations.

That’s why Obama told Senate Democrats this week that it’s more likely that there won’t be a deal.

READ: Obama: Chances of an Iran nuclear deal now lower than 50-50

“He said in the course of the negotiations he’s been more optimistic, less optimistic. And he said that the chances at this point are below 50-50,” said Sen. Dick Durbin of Illinois, the No. 2 Democrat in the Senate.

Days later, though, Kerry played the other side of expectations, telling reporters optimistically that the parties “resolved some of the things that were outstanding” and that “it’s safe to say that we have made progress today.”

Because ultimately, the U.S. needs to keep not just Iran, but its partners, in the negotiations pressing full steam ahead at the negotiating table.

The coalition of five world powers – Russia, China, Germany, France and the UK – negotiating alongside the U.S. is already showing signs of strain, as Russia adopts a stance on relaxing sanctions more in line with Iran’s. In particular, the new Iranian demand that the arms embargo on it be lifted has caused frustration for the U.S. while winning support from Moscow.

On Thursday, Russian Foreign Minister Sergey Lavrov indicated that his country was backing Iran’s bid to lift the arms embargo “as soon as possible.” Russia is a top supplier of weapons to Iran.

For that, Americans also have a talking point.

“Under no circumstances should we relieve pressure on Iran relative to ballistic missile capabilities and arms trafficking,” Chairman of the Joint Chiefs of Staff Gen. Martin Dempsey said this week on Capitol Hill.