SHARM EL-SHEIKH, Egypt -- Secretary of State John Kerry will travel to Switzerland Sunday for a marathon round of talks with Iran about freezing its nuclear program.
Almost sure to come up: The letter 47 Republican senators sent this week to Iran, warning that any deal will not last beyond President Obama's term.
With the clock ticking, Kerry said that this is the last chance. He has until the end of March to hammer out a deal with Iran.
"So we believe very much that there's not anything that's going to change in April or May or June that suggests that at that time, a decision you can't make now will be made then," Kerry said. "If it's peaceful, let's get it done. And my hope is that in the next days, that will be possible."
The wild card is whether hard-liners at home scuttle the deal.
This week, Iran's supreme leader questioned whether Mr. Obama has the power to implement an agreement.
That, after the GOP lawmakers -- led by junior Sen. Tom Cotton -- published an open letter saying they'll make sure the deal does not hold after Mr. Obama leaves office.
It's unclear whether the letter put a potential nuclear deal in jeopardy.
"When I negotiate for the first time on Sunday night with Foreign Minister (Mohammad Javad) Zarif, I'll have a better sense of where we are," Kerry said. "But what I do know is that this letter was absolutely calculated directly to interfere with these negotiations."
Kerry said he has no plans to apologize for the Republican senators' action.
"Not on your life," Kerry said. "I'm not going to apologize for an unconstitutional, un-thought-out action by somebody who's been in the United States Senate for 60-some days. That's just inappropriate."
Kerry continued, "I will explain very clearly that Congress does not have the right to change an executive agreement."
Sunday will be the first face to face meeting since the political firestorm over the letter erupted.
Kerry told us that up to this point, negotiators have made progress on limiting Iran's nuclear technology. Now, it is time for some tough political decisions.