Sri Lanka, Jan. 4 -- Hours after a dramatic military operation ousted Venezuelan leader Nicolas Maduro from power and removed him from the country Saturday, President Donald Trump said the United States would "run" Venezuela at least temporarily and tap its vast oil reserves to sell to other nations.

U.S. operations on Saturday represented America's most assertive action to achieve regime change in a country since the nation's 2003 invasion of Iraq. The actions raise stark new questions about the legality of the U.S. moves under a broader campaign against the South American nation.

The middle-of-the-night seizure of Maduro and his wife, Cilia Flores, who were transported on a U.S. warship and arrived in New York Saturday evening to face...