The Pentagon announced on Tuesday it was temporarily suspending operational training for Saudi military studentsin the United States following a shooting rampagelast week by a Saudi air force officer.
Saudi military students in the US will continue classroom training but operational training is halted pending a security review, the US Defence Department said.
Mohammed Alshamrani, a 21-year-old lieutenant in the Saudi Royal Air Force, opened fire in a classroom at Pensacola Naval Air Station in Florida on Friday, killing three American sailorsand wounding eight other people before being shot dead by police.
Alshamrani, who was armed with a lawfully purchased Glock 9mm handgun, was reported to have posted a manifesto on Twitter before the shooting denouncing America as "a nation of evil."
The FBI said on Sunday they were investigating with the "presumption" it was an act of terrorism, as in most active shooter probes, but had yet to make a final determination.
White House National Security Advisor Robert O'Brien went further, however, saying: "To me, it appears to be a terrorist attack."
"We'll have to see what the FBI investigation shows," O'Brien added, on CBS's"Face the Nation."
The FBI's main goal, special agent-in-charge Rachel Rojas told a news conference, is to confirm whether Alshamrani "acted alone or was he a part of a larger network".
"We currently assess there was one gunman who perpetrated this attack and no arrests have been made in this case," she said.
Days after the attack, US Defence Secretary Mark Esper said he ordered a review of vetting procedures while defending the training program that brought Mohammed Alshamrani to Pensacola Naval Air Station.
In a pre-taped interview that aired on "Fox News Sunday," Esper confirmed several Saudis had been detained, including "one or two" who filmed the shooting on their cellphones.
US media also reported that Alshamrani had shown mass shooting videos at a dinner party the night before the attack.
Rojas said a number of Saudi students who were close to Alshamrani were cooperating with investigators, and the Saudi government had pledged to "fully cooperate" with the investigation.
The attack has struck a nerve in the US with its echoes of the 11 September 2001 attacks, in which Saudi citizens accounted for 15 of the 19 hijackers that flew airliners into the World Trade Centre and the Pentagon.
Saudi Arabia remains one of the closest US allies in the Middle East, and President Donald Trump has cultivated its controversial de facto ruler, Crown Prince Mohammed bin Salman.
Washington was slammed for defending Saudi Arabia in the
Trump, notoriously known for his quick-handed and unfiltered response to terror attacks around the world, fell short of labelling the Saudi gunman a terrorist, as is usually the case, but instead assured Americans of Riyadh's positionbefore the result of an investigation into the attack had been released.
"King Salman of Saudi Arabia just called to express his sincere condolences and give his sympathies to the families and friends of the warriors who were killed and wounded in the attack that took place in Pensacola, Florida," Trump said in a tweet just moments after being briefed on the situation.
"The king said that the Saudi people are greatly angered by the barbaric actions of the shooter, and that this person in no way shape or form represents the feelings of the Saudi people who love the American people," he added.
An article posted by The New York Times said Trump's "first instinct was to tamp down any suggestion that the Saudi government needed to be held to account".
"But even stranger was the president’s parroting of the Saudi line before learning the results of an investigation into whether the gunman acted alone, or had allegiances to Al Qaeda or terrorist groups," the article read.
"Trump was so quick and so eager to assure the Saudis that the relationship would continue before anyone knew how to categorise the shooting that it raised questions about how the administration would have responded if the suspect had been an Iranian, or an immigrant from Mexico," it added.
Social media users were also quick to pick up on Trump's absurd behaviour in the aftermath of the attack, which killed three military students including a Yemeni-American trainee.
"Isn't it interesting how quick Trump and Pompeo are to broadcast Saudi government condolences for the murder of three Americans and how slow they were to criticise the Saudi government's murder" of Khashoggi, Martin Indyk, a former American ambassador to Israel and Middle East negotiator tweeted.
Columnist and author Max Boot also criticised Trump's reaction to the shootings.
"A Saudi officer shot dead three Americans and wounded eight others. Instead of expressing outrage or vowing vengeance, or even waiting for all the facts, Trump sounded as if he were auditioning for the job of press secretary at the Saudi embassy," he said.