Ever since he seized power in a military takeover nearly four years ago, President Abdel Fattah el-Sisi of Egypt has been barred from the White House. But President Trump made clear on Monday that the period of ostracism was over as he hosted Mr. Sisi and pledged unstinting support for the autocratic ruler.

“We agree on so many things,” Mr. Trump said as he sat beside Mr. Sisi in the Oval Office.