Iran said Friday’s negotiations with the US could be the first stage of a longer diplomatic process, signaling there won’t be a quick resolution to escalating tensions between the two sides.

Differences over the scope for the talks have also cast doubts on whether it will still go ahead, keeping open the risk of U.S. military action.

US President Donald Trump warned that Iran’s supreme leader should be “very worried,” as both sides prepare for their first formal negotiations since the United States bombed Tehran’s nuclear program last year.

Ayatollah Ali Khamenei, Iran’s supreme leader, has vowed to unleash a regional war if America launches air strikes. Initially few in the Middle East seemed eager for further conflict. The region’s power-brokers tried to dissuade America from military action. But attitudes now look more mixed.

WASHINGTON — Top Trump administration officials do not yet have clear guidance on what President Donald Trump would hope to accomplish with military action in Iran as U.S. and Iranian officials plan to meet Friday to try to avoid a war,

Iran requested to move talks from Turkey, Secretary of State Rubio confirms. Rubio laid out what topics needed to be discussed for a "meaningful" result.

The authorities are making mass arrests, seizing assets and hunting down doctors who treated protesters. Some Iranians keep showing defiance anyway.