Kristi Noem, the homeland security secretary, said a vessel had been “apprehended.” It was the second action this month against a tanker carrying Venezuelan oil.

Closely tied to Washington during much of the Cold War, Venezuela has gone through political upheavals over the years that now make it a major enemy in the eyes of the Trump administration.

At AmericaFest, conservative leaders insulted one another, revealing serious rifts over conspiracy theories, antisemitism and who belongs in America.