Venezuelan President Nicolas Maduro addressed thousands of supporters amid U.S. pressure, declaring, "Failure is not an option."

A U.S. ground invasion is improbable, according to many analysts. From Maduro’s perspective, staying in Venezuela might be the safest way of protecting himself, his money and his family, said Moisés Naím, an analyst at the Washington-based Carnegie Endowment for International Peace.

International airlines are canceling flights to Venezuela after the U.S. Federal Aviation Administration warned pilots about security risks and increased military activity.

A key move was Washington's formal designation of the Cartel de los Soles, a network it alleges is deeply tied to top Venezuelan officials, as a terrorist organization, which came into effect on Monday. Venezuela called the label a "ridiculous scheme" intended to justify an unlawful intervention in Venezuela.

The FAA urged civilian aircraft in Venezuelan airspace to "exercise caution" due to the "worsening security situation and heightened military activity in or around Venezuela."

The Trump's administration has ramped up pressure on Venezuelan President Nicolás Maduro by designating the Cartel de los Soles as a foreign terrorist organization.

Despite this long relationship, Noriega proved to be a highly unreliable Cold War partner. While on Washington’s payroll, he supplied Castro with intelligence on U.S. operations and helped facilitate the shipment of weapons from Cuba to various Marxist insurgent groups.

The U.S. is considering dropping leaflets on Caracas as a kind of psychological warfare to pressure Venezuelan President Nicolás Maduro, multiple U.S. officials familiar with the talks told CBS News.

The U.S. declared an alleged cartel in Venezuela a terrorist organization, the latest action targeting the country and the Maduro government.