Donald Trump's election as president raises the prospect the United States will pull out of the nuclear pact it signed last year with Iran, alienating Washington from its allies and potentially freeing Iran to act on its ambitions.

Outgoing President Barack Obama's administration touted the deal, a legacy foreign policy achievement, as a way to suspend Tehran's suspected drive to develop atomic weapons. In return Obama, a Democrat, agreed to a lifting of most sanctions.

The deal, harshly opposed by Republicans in Congress, was reached as a political commitment rather than a treaty ratified by lawmakers, making it vulnerable to a new U.S. president, such as Trump, who might disagree with its terms.