Vice President Mike Pence told a conference of European and Middle East leaders on Thursday that Iran is plotting to eliminate Israel from the face of the earth, and seeks to unleash a 'new Holocaust.'

With Israeli Prime Minister Benjamin Netanyahu watching, Pence said in Poland that Tehran poses 'the greatest threat to peace and security' in the region.

Hours earlier, Secretary of State Mike Pompeo told reporters that 'confronting Iran' is a necessary step for any nation that wants to 'achieve peace and stability in the Middle East.'

'The three H's — the Houthis, Hamas and Hezbollah — these are real threats ... you can't get peace in the Middle East without pushing back against Iran,' Pompeo said, referring to the Islamic regime's proxies in Yemen, in Lebanon and in Syria and Iraq.

The U.S. and Poland cooperated in organizing the two-day conference in Warsaw.

Iranian supreme leader Ayatollah Ali Khamenei and other leaders in Tehran celebrated the 40th anniversary of the Islamic Revolution on Monday with new threats against Israel

Vice President Mike Pence warned Thursday during a conference on Peace and Security in the Middle east in Warsaw, Poland, that Iran is plotting a 'new Holocaust'

Iran celebrated the 40th anniversary of the Islamic Revolution on Monday. President Hassan Rouhani vowed to 'raze Tel Aviv and Haifa to the ground' if the U.S. military should attack.

The Trump administration responded with a video message from National Security Advisor John Bolton,' aimed squarely at Ayatollah Ali Khamenei.

'For all your boasts, for all your threats to the life of the American president, you are responsible for terrorizing your own people,' Bolton declared. 'I don't think you'll have many more anniversaries to enjoy.'

Pence on Thursday denounced a new initiative by France, Germany and Britain to let European businesses keep operating in Iran despite renewed U.S. sanctions designed to hamstring Iran's nuclear weapons ambitions.

'It's an ill-advised step that will only strengthen Iran, weaken the EU and creates still more distance between Europe and the United States,' Pence said.

'The time has come for our European partners to withdraw from the Iran nuclear deal and join with us as we bring the economic and diplomatic pressure necessary to give the Iranian people, the region and the world the peace, security and freedom they deserve,' he said.

(L-R) Vice President Pence, Prime Minister of Poland Mateusz Morawiecki, Israeli Prime Minister Benjamin Netanyahu and U.S. Secretary of State Mike Pompeo, from left, stood for group photos on Thursday at the two-day conference on Peace and Security in the Middle East in Warsaw, Poland

As Iran's clerical state marks 40 years since the overthrow of the pro-U.S. shah, Pence vowed maximum pressure while not explicitly urging regime change.

'As Iran's economy continues to plummet, as the people of Iran take to the streets, freedom-loving nations must stand together and hold the Iranian regime accountable for the evil and violence it has inflicted on its people, on the region and the wider world,' he said.

US sanctions 'will get tougher still' unless Iran 'changes its dangerous and destabilising behavior,' Pence said.

The European Union, including summit host Poland, has shown no sign of rejecting the 2015 accord negotiated under former US president Barack Obama in which Iran constrained its nuclear programme in return for promises of sanctions relief.

EU officials say they acknowledge concerns about Iran but believe the deal, with which Tehran has complied, is working and that the clerical state is not the only problematic actor in the region.

Pence's most fiery verbal attacks on Iran focused on the nation's status as 'the leading state sponsor of terror in the world.'

Forty years ago this month, the mullahs seized control of the country – and every year since, they have supported terrorist proxies and militias like Hezbollah, Hamas, and al Qaeda, exported missiles, and fueled conflicts in Syria and Yemen and beyond,' he said.

'Iran endlessly spews hatred against Israel, our most cherished ally. The Ayatollah Khamenei himself has said, “It is the mission of the Islamic Republic of Iran to erase Israel from the map of the region”.'