Senior US and Iranian officials are expected to meet in Oman for direct talks in the coming hours, amid a crisis that has raised fears of a military confrontation between the two countries.

The discussions come after a US military build-up in the Middle East in response to Iran's violent repression of nationwide anti-government protests last month, that human rights groups say killed many thousands of people.

Uncertainty over the location and scope had threatened to derail the talks, which are part of a diplomatic effort by regional mediators to de-escalate tensions.

Both countries remain far apart in their positions. The hope is that, if successful, the discussions could lead to a framework for negotiations.