BOGOTÁ, Colombia — Vice President Mike Pence announced additional sanctions on Venezuelan officials Monday, urged Latin American neighbors to freeze assets of the state oil company and held his first face-to-face meeting with Venezuela’s opposition leader.

Visiting Colombia, Mr. Pence also warned some countries in the region that have conspicuously sought to remain neutral in the crisis convulsing Venezuela that they cannot remain so, singling out Mexico and Uruguay.

“We believe there can be no bystanders,” he said. “No one on the sidelines of this, particularly in our hemisphere.”

The statements by Mr. Pence, who was making his fifth trip to Latin America, escalated the Trump administration’s campaign aimed at pressuring President Nicolás Maduro of Venezuela to step down.