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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

(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