* Attack knocked out 5% of global crude supply
* Source says could take weeks to resume full output
* Washington blames Iran for attack
* Yemen's Houthi movement says it was behind drone attack(Adds reaction from world governments, background onSaudi-Yemen conflict, previous DUBAI)
By Roberta Rampton and Rania El Gamal
WASHINGTON/DUBAI, Sept 15 (Reuters) - The attack on SaudiArabia's oil facilities on Saturday that has threatened globaloil supplies came from a direction indicating that Iran wasbehind it, and cruise missiles may have been the weapon ofchoice, according to a senior U.S. official.
The comments added heft to Washington’s accusation that Iranlaunched the attacks that knocked out more than 5% of global oilsupply, instead of the Yemeni Houthi group that claimed it.Tehran rejected the accusation, but said it was ready for war.
The strike on the heartland of Saudi Arabia's oil industry,which included damage to the world's biggestpetroleum-processing facility, was expected to send oil pricesup $5 to $10 per barrel on Monday and inflame tensions acrossthe Middle East.
The U.S. official, who asked not to be named, said on Sundaythere were 19 points of impact in the attack on Saudi facilitiesand that evidence showed the launch area was west-northwest ofthe targets - the direction of Iraq and Iran - not south fromYemen.
The official added that Saudi officials indicated they hadseen signs that cruise missiles were used in the attack, whichis inconsistent with the Iran-aligned Houthi group’s claim thatit conducted the attack with 10 drones.
"There's no doubt that Iran is responsible for this. Nomatter how you slice it, there's no escaping it. There's noother candidate," the official told reporters.
Iranian Foreign Ministry spokesman Abbas Mousavi dismissedthe U.S. allegation it was responsible as "pointless". A seniorRevolutionary Guards commander warned that the Islamic Republicwas ready for "full-fledged" war.
"All American bases and their aircraft carriers in adistance of up to 2,000 kilometres around Iran are within therange of our missiles," the semi-official Tasnim news agencyquoted Commander Amirali Hajizadeh as saying.
Riyadh has accused Iran of being behind previous attacks onoil-pumping stations and the Shaybah oilfield, charges thatTehran denies. Saudi Arabia has not yet blamed any party forSaturday's strike. Riyadh also says Tehran arms the Houthis, acharge both deny.
State oil giant Saudi Aramco said the attack cut output by5.7 million barrels per day, at a time when Aramco is trying toready itself for what is expected to be the world's largestshare sale.
Aramco gave no timeline for output resumption. A sourceclose to the matter told Reuters the return to full oil capacitycould take "weeks, not days".
Traders and analysts said crude may spike to as high as $100a barrel if Riyadh fails to quickly bring back supply.
Another source briefed on the developments said Saudi oilexports would continue to run as normal this week thanks tolarge storage in the kingdom, the world's top oil exporter. Itships more than 7 million barrels daily to global destinations.
Riyadh said it would compensate for the damage at itsfacilities by drawing on its stocks, which stood at 188 millionbarrels in June, according to official data. The United Statessaid it was also ready to tap emergency oil reserves if needed.
The Saudi bourse closed down 1.1% on Sunday, with bankingand petrochemical shares taking the biggest hit. Saudipetrochemical firms announced a significant reduction infeedstock supplies.
"Abqaiq is the nerve center of the Saudi energy system. Evenif exports resume in the next 24 to 48 hours, the image ofinvulnerability has been altered," Helima Croft, global head ofcommodity strategy at RBC Capital Markets, told Reuters.
'UNPRECEDENTED ATTACK'
According to the U.S. official, 17 structures at Abqaiqsuffered damage on their west-northwest facing sides, along withtwo points of impact at Saudi's Khurais facility.
U.S. Secretary of State Mike Pompeo said earlier that therewas no evidence the attack came from Yemen, where a Saudi-ledcoalition has been battling the Houthis for over four years in aconflict widely seen as a proxy war between Saudi Arabia andShi'ite Muslim rival Iran.
"Amid all the calls for de-escalation, Iran has now launchedan unprecedented attack on the world's energy supply," he said.
Some Iraqi media outlets said the attack came from there.Baghdad denied that on Sunday and vowed to punish anyone usingIraq, where Iran-backed paramilitary groups wield increasingpower, as a launchpad for attacks.
Kuwait, which borders Iraq, said it was investigating thesighting of a drone over its territory and coordinating withSaudi Arabia and other countries. The Cabinet said the primeminister ordered tighter security at vital installations.
Regional tensions have escalated since Washington quit aninternational nuclear deal and extended sanctions on Iran.
U.N. Secretary-General Antonio Guterres condemned Saturday'sattacks and called on all parties to exercise restraint andprevent any escalation.
The European Union warned that the strikes posed a realthreat to regional security, Britain called them a "recklessattempt" to disrupt global oil supplies and France said suchactions could only worsen the "risk of conflict". Iran's allyTurkey called for the avoidance of "provocativesteps".
U.S.-IRAN TALKS
The attack came after U.S. President Donald Trump said ameeting with Iranian President Hassan Rouhani was possible atthe U.N. General Assembly in New York this month. Tehran ruledout talks until sanctions are lifted.
White House adviser Kellyanne Conway did not rule out apossible meeting between the two, but told "Fox News Sunday"that the strikes "did not help" that prospect.
Saudi de facto ruler Crown Prince Mohammed bin Salman toldTrump that Riyadh was ready to deal with "terrorist aggression".A Saudi-led coalition has responded to past Houthi attacks withair strikes on the group's military sites in Yemen.
The conflict has been in military stalemate for years. TheSaudi alliance has air supremacy but has come under scrutinyover civilian deaths and a humanitarian crisis that has leftmillions facing starvation. The Houthis, more adept at guerrillawarfare, have increased attacks on Saudi cities, thwarting peaceefforts.
(Reporting by Rania El Gamal and Parisa Hafezi; Additionalreporting by Saeed Azhar and Hadeel Al Sayegh in Dubai, TimothyGardner in Washington, William James in London, John Irish inParis, Alex Lawler, Julia Payne and Ron Bousso in London, RobinEmmott in Brussels, and Michelle Nichols in New York; Writing byGhaida Ghantous and Richard Valdmanis; Editing by WilliamMaclean and Peter Cooney)