It's not an idle threat. There is a very large substantial force that's been assembled in the region.

President Trump says he'll act with speed and violence against Iran if he doesn't get a deal.

With negotiations set for Friday, can Iran talk its way out of a U.S. attack? And how much more dangerous is the world

now that the last U.S.-Russia nuclear weapons treaty has expired? This is sources and methods

from NPR. I'm Mary Louise Kelly. Each week, we go deep on the biggest national security stories in the news.

And to do that today, I want to welcome back National Security correspondent Greg Myrie.

Hey, Greg.

Hi, Mary Louise.

And science and security correspondent Jeff Brumfield, or as I like to think of him and Paris resident expert on all things, vision and fusion.

Sounds about right to me. So let's start in the Middle East. At last check, and we're recording

this just after noon, Eastern on Thursday. At last check, it looks as though U.S. and Iranian

negotiators will head to Oman on Friday tomorrow. Trump says he wants to deal

to rein in Iran's nuclear program and its military capabilities or else. Greg, start with Oman.

Why Oman? Because we were initially told they were going to get together in Istanbul.

Yeah, the Iranians wanted to move it from Turkey to

Oman. It seems the Iranians wanted that change of venue. It's a little more low-key in Oman. If it was

in Istanbul, Turkey, you'd have a lot of media, a lot of clamor, a lot of attention. I think the

Iranians didn't want that. Um, Oman is definitely

more of a low-key setting. It's a little smaller. Got it. Exactly. So I think that's it, but it shouldn't

affect the substance, really, of the talk. So let's go to the substance. And I want to ask the

how did we get here a question, but I fear that we'll end with us going all the way back

to 1953 and the U.S. engineered coup in Iran. So why don't Greg, why don't you just walk us

...