US Secretary of State John Kerry has said a speech by Iran’s supreme leader, who vowed to defy US policies despite a recent nuclear deal, was “very disturbing”.

In a speech on Saturday at a Tehran mosque, Iranian Supreme Leader Ayatollah Khamenei praised Iran for the historic deal which took 10 years in the making, but launched an attack on the United States and its Middle East policies.

To a crowd chanting “Death to America!” and “Death to Israel!”, Mr Khamenei said he would not let the nuclear deal be “abused” or “endanger Iran’s security and defence capabilities”, adding that US policies in the region of Tehran were “180 degrees” opposed to Iran’s.

Mr Khamenei said: “Whether the agreement is approved [by the US Congress and Iran’s parliament] or not, we will not stop backing our friends in the region, including the oppressed nations of Palestine, Yemen, Syria, Iraq, Bahrain and Lebanon who will continue to enjoy our support.

“Even after this deal our policy towards the arrogant US will not change.”

‘Very disturbing’

He said that American leaders sought Iran’s “surrender” and that Iran would not welcome war but if there was one, the United States would be humiliated.

Mr Khamenei’s comments, which Saudi-owned Al Arabiya television quoted, come just days after a historic Iran nuclear deal was made.

Under the agreement between Iran and major world powers, economic sanctions will be gradually lifted in return for long-term curbs on Iran’s nuclear programme.

In an interview with Al Arabiya television, Mr Kerry said: “I don’t know how to interpret it at this point in time, except to take it at face value, that that’s his policy.

“But I do know that often comments are made publicly and things can evolve that are different. If it is the policy, it’s very disturbing, it’s very troubling”.

Mr Khomeini has long-held reservations towards the west and a hostile relationship with the US since he seized power from the shah during the 1979 Islamic revolution.

Historic nuclear deal

Mr Khamenei’s remarks could also be a major blow to Iranian foreign minister Mohammad Javad Zarif and President Hassan Rouhani, who led the nuclear negotiation talks as plans are being made in the wake of the deal.

Iran and six world powers known as the P5+1 group – the US, UK, France, China and Russia plus Germany – reached a landmark agreement in Geneva last week after 12 years of talks. The west has long suspected Iran of creating a nuclear bomb and imposed heavy sanctions which have crippled the country’s economy.

Under the deal a number of these sanctions, which hit Iran’s key energy and financial sectors, will be lifted along with restricted trade, air travel and oil exports. In return, Iran must scale back its nuclear activities to ensure it cannot build a nuclear bomb. UN inspectors would also have also access to all suspect Iranian sites, including military ones, but Iran could challenge its request for access.

Negotiations between Iran and the P5+1 group began in 2006.

Hard-line opposition

The deal has largely been welcomed by world leaders who see it as a progressive move for Iran. President Obama called it a “comprehensive deal” while President Rouhani said it was a “new chapter” for Iran.

However, the deal has also been widely criticised by US Republicans who see it as flawed and are not confident it will stop Iran from getting nuclear weapons.

Israeli Prime Minister Binyamin Netanyahu has led criticism of the agreement, declaring it a “historic mistake for the world”.

Iranian hardliners also feel demoralised by the compromises Iran has made, and regard its nuclear programme as a great achievement.

The Gulf countries, as Sunni Arab states, resent the growing power of Shia Iran and have long accused Tehran of interference, alleging financial or armed support for political movements in countries including Bahrain, Yemen and Lebanon.

Mr Kerry said the US believed its Arab allies had the ability to confront Iranian interference in the region.

“I think President Obama’s belief and our military assessments, our intelligence assessments, are that if they organise themselves correctly, all of the Arab states have an untapped potential that is very, very significant to be able to push back against any of these activities,” he said.