In that view, Mr. Trump, by strongly embracing the Saudis, pulled the gloves off a brawl that had long threatened to turn ugly. But it could also end up hurting American efforts to build broader coalitions in the region, and weaken an ally that has provided a vital base for the American military in its campaign against the Islamic State.
Randa Slim, at the Middle East Institute in Washington, said the move raised questions about whether the Trump administration knew what it was unleashing when it further empowered the Saudis.
“Regionally, the decks are stacked against Qatar: If denied U.S. support, the Qatari emir has no option but to back down,” Ms. Slim said. “The question is what, if anything, will this administration do about it?”
Signaling concern, Secretary of State Rex W. Tillerson offered to broker the impasse on Monday. “We certainly would encourage the parties to sit down together and address these differences,” Mr. Tillerson said.
The move was announced by Saudi Arabia, the United Arab Emirates, Egypt, Bahrain and Yemen. The Maldives and the eastern government in divided Libya also said they were joining in the sanctions. But in a sign that some Saudi allies were still on the fence, neither Jordan nor Kuwait joined in.
