Tehran, September 17: Iran's supreme leader on Tuesday ruled out negotiations with the US "at any level", as tensions mounted between the arch-foes after Washington blamed Tehran for weekend attacks on Saudi oil installations. Yemen's Iran-aligned Huthi rebels claimed responsibility for Saturday's attacks, which halved oil output in Saudi Arabia, the world's top crude exporter.

But on Tuesday, a US official upped the pressure on Tehran, telling AFP the strike was launched from Iranian soil and that cruise missiles were involved. Drone Attacks on Saudi Oil Installations: Iran Dismisses US Accusations.

The official, who asked to remain anonymous, said the US was gathering evidence to present to the international community at the UN General Assembly next week.

US Vice President Mike Pence said Secretary of State Mike Pompeo would travel Saudi Arabia on Tuesday to "discuss our response".

Earlier in the day, Ayatollah Ali Khamenei said the US had adopted a policy of "maximum pressure" on Iran because it believes it cannot bring the Islamic republic to its knees through other means.

"The policy of 'maximum pressure' against the Iranian nation is worthless and all Islamic Republic of Iran officials unanimously believe there will be no negotiations with the US at any level," he said in a televised address.

Tensions pitting Iran against the US and its allies have threatened to boil over since May last year when President Donald Trump abandoned a 2015 nuclear deal and began reimposing sanctions in a campaign of "maximum pressure".

Iran responded by scaling back its commitments under the landmark accord, which gave it the promise of sanctions relief in return for limiting the scope of its nuclear programme.

- Iran accused -

Trump said the US was ready to help Saudi Arabia after the attacks that halted about six percent of the world's oil supply and triggered a record leap in crude prices.

"I'm not looking to get into new conflict, but sometimes you have to," he said. "That was a very large attack, and it could be met by an attack many, many times larger."

"Certainly, it would look to most like it was Iran," Trump added.

US Secretary of Defence Mark Esper also labelled Iran a destabilising force in the region, but stopped short of directly accusing Tehran over the strikes.

The US military, he said, was working with its partners to "address this unprecedented attack and defend the international rules-based order that is being undermined by Iran".

A day after the attacks, the White House had said Trump could meet his Iranian counterpart Hassan Rouhani on the sidelines of the UN General Assembly in New York next week.

Rouhani has already rejected the possibility of direct negotiations with the US unless it lifts all sanctions.

The Iranian president has said that even if that happens, any talks must be held in the framework of the nuclear accord.

- US must 'repent' -

Khamenei reiterated this on Tuesday, saying that if the US "repents" and returns to the Joint Comprehensive Plan of Action, then it can talk to Iran along with other parties to the deal.

"If the US takes back its words and repents after pulling out of the JCPOA... then it can join the other countries party to the JCPOA and talk to Iran along with the other countries," he said, using the agreement's formal title.

"Without this, no negotiations will happen at any level between the Islamic Republic of Iran's officials and the Americans, not during the visit to New York or any other visit."

Yemen's Huthi rebels claimed responsibility for Saturday's attacks on Abqaiq, the world's largest oil processing facility, and the Khurais oil field in eastern Saudi Arabia.

Oil prices receded five percent on Tuesday, reversing some of the previous day's gains as analysts said they were expecting Saudi output to recover sooner than expected after the weekend's attacks.

The Huthis said 10 of their drones struck the sites, but Saudi Arabia pointed the finger of blame at Iran.

"All indications are that weapons used in both attacks came from Iran" rather than Yemen, said Turki al-Maliki, spokesman for a Saudi-led military coalition fighting the rebels.

Rouhani said the attacks were an act of self-defence by the Huthis against the coalition, which has been bombing them since 2015 in support of Yemen's internationally recognised government.

As aftershocks continued to ripple across financial markets on Tuesday, energy specialists S&P Platt said around three million barrels per day of Saudi crude would remain offline for at least a month.

Britain and Germany on Tuesday urged the international community to forge a "collective response" to the attacks.

French Foreign Minister Jean-Yves Le Drian, visiting Cairo, said it was "imperative to put all our efforts together to achieve this de-escalation".

China condemned the attacks and appealed to all sides to "refrain from taking actions that lead to an escalation of tensions in the region".

(The above story first appeared on LatestLY on Sep 17, 2019 10:19 PM IST. For more news and updates on politics, world, sports, entertainment and lifestyle, log on to our website latestly.com).