Iranian President Hassan Rouhani speaks during a press conference in New York on September 26, 2019
Iranian President Hassan Rouhani speaks during a press conference in New York on September 26, 2019 AFP / Kena Betancur

Tensions between the United States and Iran escalated on Thursday as Washington deployed more troops to the Gulf and Tehran challenged its arch-enemy to provide evidence it attacked Saudi oil facilities.

The Pentagon announced it was sending 200 troops with Patriot missiles to bolster Saudi Arabia's defenses following the strikes this month that knocked out half of the Kingdom's oil production.

After a week of diplomacy at the United Nations where European leaders unsuccessfully tried to arrange a US-Iran meeting, Iranian President Hassan Rouhani demanded that Washington back up its accusations that Iran was behind the attacks.

"Those who make the allegations must provide the needed proof. What is your evidence?" he told reporters.

Tensions between Iran and the United States have soared since President Donald Trump pulled out of a 2015 international deal that was meant to lift sanctions in exchange for a commitment from Tehran that it would cease trying to develop nuclear weapons.

The United States, France, Germany, Britain and Saudi Arabia have all, to varying degrees, blamed Iran for the brazen September 14 air strikes on the kingdom's Abqaiq plant and Khurais oil field.

Secretary of State Mike Pompeo said the United States shared evidence on the attacks with other countries during the UN General Assembly.

"I think now it has struck them how clear it is that the Islamic Republic of Iran is not prepared to do the right thing and behave like a normal nation," Pompeo told reporters Thursday.

Iran "used their usual method of trying to obscure this through use of a proxy force. They had to know it was the case that the world would rally against them, and yet they still chose to do it," he added.

Tehran has blasted the allegations as "ridiculous." It denies responsibility, and the attacks have been claimed by Yemen's Iranian-backed Huthi rebels.

"If you do have any evidence or documentation please do make them available to me," Rouhani said.

He said that Western powers should instead stop arming Saudi Arabia in its offensive in Yemen, which the United Nations calls the world's biggest humanitarian crisis.

'Vile and cowardly regime'

A senior Saudi official, in an address to the United Nations General Assembly, urged a united front against Iran.

"It is a vile and cowardly regime, which hides behind its affiliated militias, pushing them to claim responsibility," said Adel al-Jubeir, the minister of state for foreign affairs.

"This regime is only checked by a firm and unified stand and the application of maximum and sustained pressure until it desists from its terrorist behavior," he said.

The US president reimposed economic sanctions and in May his administration said it would unilaterally force all countries to stop buying Iran's oil, one of Tehran's main sources of wealth.

Tehran soon afterward shot down an unmanned US drone. At the very last minute, Trump stepped back from striking Iran in June as the risk of all-out war in the Middle East seemed all too real.

In its latest move to ratchet up pressure, the United States banned senior Iranian regime figures and their families from entering the United States.

It came 24 hours after Washington announced it would punish Chinese companies that bought Iranian oil, on the last official day of Trump's participation at the UN General Assembly.

The US Defense Department said the troop deployment would involve one battery of surface-to-air missiles, along with four Sentinel radars used for air and missile defense systems.

And the UN's nuclear watchdog confirmed Thursday that Iran has started using advanced models of centrifuges to enrich uranium, in a new breach of the agreement with world powers.

No meeting at UN

Speculation had been rife that Trump might meet Rouhani on the sidelines of the UN summit but the US leader returned to Washington without a rendezvous taking place.

Rouhani said Thursday that Iran would be willing to hold talks with the United States if Trump lifted sanctions and ended his policy of "maximum pressure" on Tehran.

"If we reach a time when these preconditions are taken off the table, of course the possibility exists to talk with America," he said at the news conference.

French President Emmanuel Macron had shuttled between his US and Iranian counterparts over two days at the UN, trying to arrange an encounter.

"There was a narrow path. That path has shrunk, but it's still there," a French diplomat said.