Donald Trump ally Giuliani says end is near for Iran's rulers

US President Donald Trump will suffocate Iran's "dictatorial ayatollahs," his close ally Rudy Giuliani said on Saturday, suggesting his move to re-impose sanctions was aimed squarely at regime change.

The former New York mayor who is now Trump's personal lawyer was addressing a conference of the Paris-based National Council of Resistance of Iran (NCRI), an umbrella bloc of groups of exiled Iranians opposed to the Islamic Republic.

Giuliani said the US is now realistically seeing "an end to the regime of Iran," pointing to recent protests in the country sparked by a currency collapse after Trump pulled out of the 2015 nuclear deal.

At the same conference last year, John Bolton, who was appointed Trump's National Security Advisor in April this year, told NCRI members they would be ruling Iran before 2019.

European countries which signed the 2015 Iran deal along with the United States, Russia and China, are sticking with it, saying the agreement prevents Iran developing weapons-grade nuclear fuel. But Giuliani said Europe should be "ashamed" of itself.

In Tehran, supreme leader Ayatollah Ali Khamenei said Trump would fail in any attempt to turn the Iranian people against the ruling system.