US and Iranian officials are set to hold a third round of indirect talks in Switzerland today [Thursday], in a move that could avert a potential attack by President Trump.

President Donald Trump has threatened to strike Iran if a nuclear deal is not reached.

The talks come as the US military is deploying its largest military force in the Middle East since the 2003 invasion of Iraq, and has warned Iran it will respond if it attacks.

The talks are seen as a last-ditch effort to avert a conflict, but there is little clarity on the prospects for an agreement.

While Trump has said he prefers to resolve the crisis diplomatically, he has also said he is considering a limited attack on Iran to pressure its leaders to accept the deal.

Donald Trump has made little effort to explain what he wants from the negotiations and why military action might be necessary now.

The US struck Iranian nuclear facilities during a 12-day war between Iran and Israel in June last year.

Iran has rejected US demands that it halt uranium enrichment within its borders.