US National Security Adviser says Iran will face consequences if it crosses his country and allies amid war of words.

The US national security adviser has launched a scathing attack on Iran saying there will “be hell to pay” if Tehran tried to harm the US and its allies.

The warning from John Bolton came after US President Donald Trump and his Iranian counterpart Hassan Rouhani clashed at the United Nations General Assembly on Tuesday.

“So, I might imagine they would take me seriously when I assure them today that if you cross us, our allies or our partners, if you harm our citizens, if you continue to lie cheat and deceive. Yes, there will indeed be hell to pay,” the US national security adviser said.

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Speaking at an organisation that opposed the 2015 nuclear deal with Iran, from which the Trump administration withdrew in May, Bolton criticised the deal as “the worst diplomatic debacle in American history”.

“[The deal] did nothing to address the regime’s destabilising activity or its ballistic missile development and proliferation,” Bolton said.

“Worst of all the deal failed to achieve its fundamental objective permanently denying Iran all paths to nuclear weapons.”

JCPOA members set up payment system

Earlier, Trump, during his speech at the General Assembly, called Tehran “the leading sponsor of terrorism” while Rouhani accused the US administration of trying to overthrow his government.

The other five major powers that signed the Iran deal, known as the Joint Comprehensive Plan of Action (JCPOA) under which Iran agreed to curb nuclear programme in exchange for sanctions relief, have made it clear that they remain committed to it.

Top diplomats from France, Britain, Germany, China and Russia agreed to establish a financial facility in the European Union to facilitate payments for Iranian imports and exports including oil.

US Secretary of State Mike Pompeo hit back at these countries for attempting to subvert US sanctions, saying that they were bolstering Iran as the “number one state sponsor of terror”.

“I was disturbed and indeed deeply disappointed to hear remaining parties in the deal announced they are setting up a special payment system to bypass US sanctions,” he said.

“This is one of the most counterproductive measures imaginable for regional and global peace and security.”

Since its withdrawal from the Iran deal, the Trump administration has slapped biting sanctions on Tehran in order to choke its oil exports – the main source of income for the Islamic Republic.

Some of Tehran’s biggest oil customers appear to have succumbed to the US pressure, with India – a major buyer of Iranian oil – cutting down on its imports.

The US Department of State has spelled out a campaign of “maximum economic and diplomatic pressure” to drive Iran towards negotiating a “better” deal to replace the Iran nuclear deal.

In his UN speech, Rouhani said the US sanctions are “economic terrorism”.