Iran's supreme leader has said the US would overthrow the Iranian government if it could, adding that the country had a "controlling and meddlesome" attitude towards the Islamic Republic.

In a speech to mark the 35th anniversary of the 1979 Islamic revolution on Saturday, Ayatollah Ali Khamenei said that the US is fundamentally Iran's enemy, even as he defended his country's ongoing talks to settle a decade-old dispute about the Islamic Republic's nuclear programme.

"American officials publicly say they do not seek regime change in Iran," Khamenei told army officers in Tehran.

"That's a lie. They would not hesitate a moment if they could do it."

But Iran's most powerful leader also called on critics of President Hassan Rouhani to be fair and give him time, to pursue his policy of engagement with the outside world, including the US and the EU.

"No more than a few months have passed since the [Rouhani] government took office," he said in comments posted in his website, leader.ir.

"Authorities should be given the opportunity to push forward strongly. Critics should show tolerance towards the government."

Earlier this week, Ayatollah Mohammad Taqi Mesbah Yazdi, a prominent religious leader, accused Rouhani of selling Iran's "dignity" under the Geneva deal.

Khamenei's support is crucial for Rouhani's diplomatic success in negotiations.

Possible motive

Khamenei made no direct mention of the talks between Iran and world powers, but he said that in dealing with "enemies", Iran should be prepared to change tactics but not compromise on its main principles.

Speaking to Al Jazeera, Sadegh Zibakalam, politics professor at Tehran University, wondered if Khamenei was trying to appease the country's hardliners, who are critical of Rouhani.

"Maybe the Supreme Leader, by using those harsh words against the United States, is trying to calm down those hardliners," he said.

Khamenei urged Iran not to pin hopes for economic recovery on the sanctions relief from the landmark interim deal signed on November 24.

"The only solution to the country's economic problems is to employ [Iran's] infinite domestic capacities, not to pin hopes on the lifting of sanctions," he said.

"No expectations from the enemy."

The deal is the centerpiece of Rouhani's policy.

Iran in January stopped enriching uranium to 20 percent and started neutralising its existing stockpile of that grade, just steps away from weapons material, in order to fulfil commitments reached under the interim deal.

In return, the US and the EU simultaneously announced the lifting of sanctions on petrochemical products, insurance, gold and other precious metals, auto industry, passenger plane parts and services.

They also plan to release $4.2bn Iranian assets of oil revenues blocked overseas, in eight installments over a period of six months.

The first installment of $550m was provided to Iran on February 1.