* 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 (Wraps up latest developments, including comment from U.S. official)
By Rania El Gamal and Parisa Hafezi
DUBAI, Sept 15 (Reuters) - The attack on Saudi Arabia's oil facilities on Saturday that has threatened global oil supplies came from the direction of Iran, and cruise missiles may have been used, according to a senior U.S. official.
The comments added heft to Washington’s accusation that Iran was behind the attacks that knocked out more than 5% of global oil supply, instead of the Yemeni Houthi group that claimed it. Tehran has rejected the accusation, but said it was ready for war.
The U.S. official, who asked not to be named, said there were 19 points of impact in the attack on Saudi facilities and that evidence showed the launch area was west-northwest of the targets - the direction of Iran - not south from Yemen.
The official added that Saudi officials had indicated they had seen signs that cruise missiles were used in the attack, which is inconsistent with the Iran-aligned Houthi group’s claim that it conducted the attack with 10 drones.
"There's no doubt that Iran is responsible for this. No matter how you slice it, there's no escaping it. There's no other candidate," the official told reporters.
The attack on plants in the heartland of Saudi Arabia's oil industry, including the world's biggest petroleum-processing facility, was expected to send oil prices up $5 to 10 per barrel on Monday as tensions rise in the Middle East.
Iranian Foreign Ministry spokesman Abbas Mousavi dismissed the U.S. allegation it was responsible as "pointless". A senior Revolutionary Guards commander warned that the Islamic Republic was ready for "full-fledged" war.
"All American bases and their aircraft carriers in a distance of up to 2,000 kilometres around Iran are within the range of our missiles," the semi-official Tasnim news agency quoted Commander Amirali Hajizadeh as saying.
State oil giant Saudi Aramco said the attack cut output by 5.7 million barrels per day, at a time when Aramco is trying to ready itself for what is expected to be the world's largest share sale.
Aramco gave no timeline for output resumption. A source close to the matter told Reuters the return to full oil capacity could take "weeks, not days".
Another source briefed on the developments said Saudi oil exports would continue to run as normal this week thanks to large storage in the kingdom.
Reporting by Rania El Gamal and Parisa Hafezi; Additional reporting by Saeed Azhar and Hadeel Al Sayegh in Dubai, Timothy Gardner in Washington, William James in London, John Irish in Paris, Alex Lawler, Julia Payne and Ron Bousso in London, Robin Emmott in Brussels, and Michelle Nichols in New York; Writing by Ghaida Ghantous and Richard Valdmanis; Editing by William Maclean and Peter Cooney