"If Iran gets a nuclear weapon, there are a lot of other regimes, some friendly, some not so friendly, who would get nuclear weapons after them," Vance said.

The latest round of negotiations on Tehran's nuclear program has ended without a breakthrough, and the threat of US military action still looms large. The ball seems to be back in Iran's court.

The talks come as the U.S. ramps up its military presence in the Middle East and Iran holds large-scale maritime exercises.

The US announced visa restrictions on Iranian officials and executives for repressing recent anti-regime protests and cutting off internet access, as the Trump administration ratchets up pressure on Tehran amid ongoing nuclear talks.

Iran’s Foreign Minister Abbas Araghchi has confirmed that Iran and the United States will hold nuclear talks in Oman’s capital, Muscat, on Friday

Iranian and American negotiators departed their indirect talks in Geneva with an agreement to keep talking, doing little to ease fears of an impending regional war.

Iran and the U.S. continued trading threats and warnings even as negotiators sat down to try and strike a deal to avoid a war.

A war between the United States and Iran is looming — and there are several factors suggesting President Trump might push the button soon. The big picture: Trump has been trying to strike a nuclear deal with Iran since he retook the White House last year.