By Phil Stewart and Idrees Ali
WASHINGTON, Sept 20 (Reuters) - U.S. President Donald Trumpon Friday approved sending American troops to bolster SaudiArabia's air and missile defenses after the largest-ever attackon the kingdom's oil facilities, which Washington has squarelyblamed on Iran.
The Pentagon said the deployment would involve a moderatenumber of troops - not numbering thousands - and would beprimarily defensive in nature. It also detailed plans toexpedite delivery of military equipment to both Saudi Arabia andthe United Arab Emirates.
Reuters has previously reported that the Pentagon wasconsidering sending anti-missile batteries, drones and morefighter jets. The United States is also consideringkeeping an aircraft carrier in the region indefinitely.
"In response to the kingdom's request, the president hasapproved the deployment of U.S. forces, which will be defensivein nature and primarily focused on air and missile defense,"U.S. Defense Secretary Mark Esper said at a news briefing.
"We will also work to accelerate the delivery of militaryequipment to the kingdom of Saudi Arabia and the UAE to enhancetheir ability to defend themselves."
The Pentagon's late Friday announcement appeared to closethe door to any imminent decision to wage retaliatory strikesagainst Iran following the attack, which rattled global marketsand exposed major gaps in Saudi Arabia's air defenses.
Trump said earlier on Friday that he believed his militaryrestraint so far showed "strength," as he instead imposedanother round of economic sanctions on Tehran.
"Because the easiest thing I could do, 'Okay, go ahead.Knock out 15 different major things in Iran.' ... But I’m notlooking to do that if I can," Trump told reporters at the WhiteHouse.
But the deployment could further aggravate Iran, which hasresponded to previous U.S. troop deployments this year withapprehension. It denies responsibility for the attack on SaudiArabia.
Yemen's Iran-aligned Houthi movement, which has beenbattling a Saudi-led military coalition that includes the UAE,has claimed responsibility for the strikes.
ATTACK LAUNCHED FROM IRAN?
Relations between the United States and Iran havedeteriorated sharply since Trump pulled out of the Iran nuclearaccord last year and reimposed sanctions on its oil exports.
For months, Iranian officials issued veiled threats, sayingthat if Tehran were blocked from exporting oil, other countrieswould not be able to do so either.
However, Iran has denied any role in a series of attacks inrecent months, including bombings of tankers in the Gulf andstrikes claimed by the Houthis.
U.S. officials, speaking on condition of anonymity, havefingered southwest Iran as the staging ground for the attack, anassessment based at least in part on still-classified imageryshowing Iran appearing to prepare an aerial strike.
They have dismissed Houthi claims that the attacksoriginated in Yemen.
One of the officials told Reuters the strike may have beenauthorized by Iran's Supreme Leader Ayatollah Ali Khamenei.
The United States is wary of getting dragged into anotherconflict in the Middle East. It has troops positioned in Syriaand Iraq, two countries where Iranian influence is strong andIran-backed forces operate openly.
U.S. officials fear Iran's proxies might attempt to strikeAmerican troops there, something that could easily trigger abroader regional conflict.
Saudi Arabia has said it was attacked by a total of 25drones and missiles, including Iranian Delta Wing unmannedaerial vehicles (UAV) and "Ya Ali" cruise missiles.
U.S. Marine General Joseph Dunford, chairman of the JointChiefs of Staff, said officials were still hammering out thebest array of capabilities to defend Saudi Arabia, noting thedifficulty combating a swarm of drones.
"No single system is going to be able to defend against athreat like that, but a layered system of defensive capabilitieswould mitigate the risk of swarms of drones or other attacksthat may come from Iran," Dunford said.(Reporting by Phil Stewart, Idrees Ali, Eric Beech and MohammadZargham Editing by Chizu Nomiyama and Cynthia Osterman)