Iran’s Foreign Ministry has denied any involvement in the attacks on Saudi oil facilities in an official letter to the U.S.

“Iran has nothing to do with the attack,” states the letter, which was delivered to the U.S. via the Swiss embassy in Tehran.

Switzerland represents Washington’s diplomatic interests in Iran.

“If action is taken against Iran, we will promptly retaliate and the dimensions would not be limited,” Tehran wrote in the letter, according to parts of it published by Iranian news agency IRNA on Wednesday.

The letter was delivered to the Swiss embassy on Monday, according to IRNA.

Tensions in the Middle East have escalated following drone attacks on two major oil facilities in Saudi Arabia.

The pre-dawn attacks on Saturday knocked out more than half of crude output from the world’s top exporter – five per cent of the global oil supply – and cut output by 5.7 million barrels per day.

Yemen’s Houthi rebels, who have been locked in a war with a Saudi-UAE-led coalition since 2015, claimed responsibility for the attacks, warning Saudi Arabia that their targets “will keep expanding”.

But U.S. Secretary of State Mike Pompeo swiftly accused Iran of being behind the assault, without providing any evidence.

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The claim was rejected by Tehran which said the allegations were meant to justify actions against it.

Saudi Arabia, meanwhile, has promised to “confront and deal with this terrorist aggression”, while U.S. President Donald Trump hinted at possible military action after Riyadh concluded its investigation into the attacks.

The U.S. Mission to the United Arab Emirates said that Mr Pompeo would meet Saudi Arabia’s Crown Prince, Mohammed bin Salman, in Jeddah to discuss the attack and coordinate efforts against “Iranian aggression”.

Mr Pompeo will then travel to the UAE capital Abu Dhabi to meet with its crown prince, Mohammed bin Zayed, and discuss regional and bilateral issues, it added. (dpa/NAN)