WEST PALM BEACH, Fla. — President Trump on Thursday rebuffed the C.I.A. over its conclusion that the Saudi crown prince was responsible for the killing of Jamal Khashoggi, saying the agency merely had “feelings” on the matter, and he threatened to close the entire southern border if a caravan that is so far waiting patiently on the Mexican side grows “uncontrollable.”

Mr. Trump made the remarks as he fielded questions from reporters at his Florida estate, Mar-a-Lago, expanding on the grievances that have filled his Twitter feed over the past few days. The exchange was a notable deviation on a Thanksgiving that was otherwise almost an exact replica of how the president, a known creature of habit, spent the holiday last year.

There were the early-morning tweets, this year attacking perceived judicial adversaries. There was the address to American troops stationed around the world, delivered from an opulent room at Mar-a-Lago, which he has deemed “the southern White House.” There was the visit to a Coast Guard station, where he raved about the Guard’s rising “brand.” And there was his expression of thanks for his family and for his “having made a tremendous difference in this country.”

Mr. Trump’s dispute with his own intelligence agencies over the killing of Mr. Khashoggi, an opinion columnist for The Washington Post, trailed him into the holiday weekend. The president doubled down on his insistence that an alliance with Saudi Arabia, sweetened by low oil prices and billions in investment, had more value than repercussions for any culpability in the murder of Mr. Khashoggi.

