Iran nuclear deal: What's at stake for U.S., allies?

President Trump said Wednesday at the United Nations that he has made a decision about whether to keep or kill the Iran nuclear deal he called an "embarrassment to the United States."

But he's not saying what that decision is. In the meantime, here's what you need to know about the Iran nuclear agreement: 

What is the Iran nuclear agreement? 

In 2015, President Barack Obama signed off on an agreement with the United Kingdom, France, Russia, China, Germany and the European Union in which Iran agreed to give up the means to make nuclear weapons. 

More:Trump says he's made a decision on Iran nuclear deal – but won't say what it is

More:Iran's Rouhani condemns Trump at United Nations

As part of the agreement, the U.S. and its allies would reduce long-term economic sanctions on Tehran.

Why is the deal back in the news now?

Trump now faces an Oct. 15 deadline to tell Congress whether he intends to re-certify the deal or get rid of it. 

The other signatories have said Iran is complying with the agreement, and that voiding it would only encourage Iran's nuclear weapons program, and could possibly trigger an arms race throughout the Middle East.

Killing the deal would be a "grave mistake," French President Emmanuel Macron said during his speech to the U.N. General Assembly on Tuesday.

What happens if Trump chooses to kill the deal? 

If Trump chooses not to re-certify the deal, that alone may not completely scrap the agreement. Congress would still have 60 days to decide whether or not to re-impose sanctions.

What has candidate Trump said about the Iran nuclear deal? 

During the presidential campaign, Donald Trump strongly condemned the Iran nuclear agreement negotiated by President Barack Obama. He has called it "one of the dumbest deals I've ever seen," "amateur hour" and "a disaster." 

His first priority as president, Trump promised, would be to "dismantle" it.