Iran is prepared for the resumption of talks with the United States, but they should be fair and not include Iran's defence capabilities, Iran's chief diplomat said on Friday, as regional powers work to prevent military conflict between the two foes.

US President Donald Trump said on Thursday he planned to speak with Iran, even as the US sent another warship to the Middle East and the Pentagon chief said the military would be ready to carry out whatever the president decided.

US-Iranian tensions have soared in recent weeks after a on protests across Iran by its clerical authorities.

One of the main US demands as a condition for resuming talks with Iran is curbing its missile programme, a senior Iranian official told Reuters last week. Iran rejects that demand.