Top Iranian and U.S. negotiators will resume talks on Sunday to address disputes over Tehran's nuclear programme, in a push for progress as Washington hardens its stance ahead of U.S. President Donald Trump's Middle East visit.

After initial success in April, the talks in May have hit a snag. It is not clear if things can be salvaged this week.

US Special Envoy Steve Witkoff warned that if Sunday’s talks with Iran are not productive, “then they won’t continue and we’ll have to take a different route.”