Iran denied Monday it was hit by a US cyber attack as Washington was due to tighten sanctions on Tehran in a standoff sparked by the US withdrawal from a nuclear deal.

Both nations say they want to avoid going to war, but tensions have spiralled as a series of incidents, including tanker attacks and the shooting down of a US drone by Iran in the Gulf, raised fears of an unintended slide towards conflict.

The denial came as US Secretary of State Mike Pompeo arrived in Saudi Arabia for talks on the tensions with Iran and was also due to visit the United Arab Emirates for similar discussions.