U.S. President Donald Trump on Wednesday struck a cautious note, saying there were many options short of war with Iran, which denies involvement in the Sept. 14 strikes that initially halved Saudi oil output. He ordered increased sanctions on Tehran.

“This is an attack of a scale we’ve just not seen before,” Pompeo told reporters before landing in Jeddah for talks with Crown Prince Mohammed bin Salman. “The Saudis were the nation that were attacked. It was on their soil. It was an act of war against them directly.”

The Saudi ambassador to Berlin said “everything is on the table”, telling Deutschlandfunk radio that options need to be discussed carefully.

Riyadh, which described the assault has as a “test of global will”, on Wednesday displayed the remnants of 25 Iranian drones and missiles it said were used in the strike as undeniable evidence of Iranian aggression.

The United Arab Emirates on Thursday followed its main Arab ally Saudi Arabia in announcing it was joining a global maritime security coalition that Washington has been trying to build since a series of explosions on oil tankers in Gulf waters in recent months that were also blamed on Tehran.

Yemen’s Iran-aligned Houthi movement, which is battling a Saudi-led military coalition, claimed responsibility for the assault on two Saudi oil plants, including the world’s largest processing facility. U.S. and Saudi officials rejected the claim, saying the attack had not come from the south.

The Houthis on Wednesday said they had listed dozens of sites in the UAE, the Middle East’s financial and tourism hub, as possible targets, a threat that could further strain a tense political atmosphere in the region.

Fellow Gulf OPEC producer Kuwait, which said earlier this week it was investigating the detection of a drone over its territory, has put its oil sector on high alert and raised security to the highest level as a precautionary measure.

Pompeo headed to the UAE on Thursday for talks with Abu Dhabi’s crown prince after meeting Saudi Arabia’s de facto ruler Crown Prince Mohammed on Wednesday.

“These subversive attacks aim to destabilize the region’s security and damaging the global energy supply and the global economy,” state media quoted Prince Mohammed as telling Pompeo.

Oil prices, which soared following the attack, steadied after Saudi Arabia pledged to restore full production by the end of the month.

INTERNATIONAL INVESTIGATION

Proof of Iranian responsibility, and evidence that the attack was launched from Iranian territory, could pressure Riyadh and Washington, which want to curb Iranian influence in the region, into a response. Trump has previously said he does not want war and is coordinating with Gulf and European states.

Pompeo said the attacks would be a major focus of next week’s annual U.N. General Assembly meeting and suggested Riyadh could make its case there.

“There is an international investigation, let’s wait for its results,” France’s foreign minister Jean-Yves Le Drian told C News television, adding that the General Assembly meeting presented an opportunity to de-escalate tensions.

The French army spokesman said it sent seven experts to Saudi Arabia to join the investigation. U.N. officials monitoring sanctions on Iran and Yemen are also helping probe the attack, which exposed gaps in Saudi air defenses despite billions spent on Western military hardware.Slideshow (2 Images)

U.S. efforts to bring about a U.N. Security Council response looked unlikely to succeed as Russia and China have veto powers and were expected to shield Iran.

Tehran has said the U.S. accusations were part of Washington’s “maximum pressure” policy on the Islamic Republic to force Iran to renegotiate a 2015 nuclear deal with world powers, which Trump exited last year, reimposing sanctions.

Washington and its Gulf allies want Iran to stop supporting regional proxies, including in Yemen, Iraq and Lebanon, as well as to put more limitations on its nuclear and missile programs.

The UAE, Saudi Arabia’s main partner in the Western-backed, Sunni Muslim coalition fighting in Yemen, has scaled down its military presence there as rising Iran tensions risk a war in the Gulf and as Western allies pressed for an end to the war.

The conflict, seen as proxy war between Saudi Arabia and Iran, has killed tens of thousands and pushed millions to the brink of famine. Some Western countries such as Germany have halted weapons sales to Saudi Arabia over the ruinous war.