Ten EU countries have yet to announce their position.
Pope Francis on Tuesday expressed willingness for the Vatican to mediate Venezuela's mounting crisis if both sides seek it. Russia, which along with China has backed Maduro in the crisis, underscored its view that the crisis can be resolved only with negotiations between the government and opposition.
Last week, the UN chief met with Mexico's ambassador to the UN Juan Jose Gomez Camacho who said the Montevideo conference was to "offer a chance for dialogue to all parties involved".
But President Maduro shows no sign of budging.
In a statement, it accused them of submitting to a USA "strategy to overthrow the legitimate government" and singled out Spain, which had previously led mediation efforts, for acting "cowardly".
The 16 countries are - Austria, Czech Republic, Denmark, Germany, Estonia, Finland, France, Latvia, Lithuania, Luxembourg, the Netherlands, Poland, Portugal, Spain, Sweden, and the UK.
"The government of Venezuela needs to open the borders, that's it: Open the borders and let food convoys come into your country, open up your airports and let food flights fly in", said Graham, who said he spoke to U.S. President Donald Trump about the situation in December. Norway, not an European Union member, said it also was not recognizing him.
While the USA never ruled out a military option to support Juan Guaidó's claim to power, so far Washington has called for a peaceful transition of power in the Latin American country.
The United States is sending food and medical supplies to Colombia's border with Venezuela where it will be stockpiled until it can be delivered to the economically shattered nation, USA officials with knowledge of the plan said today.
In an exclusive interview with RT, he addresses what he deems to be obvious motives behind the USA clamor to replace him with opposition leader Juan Guaido. The U.S. was among the first major powers to recognize Guaido last week. Guaido urged Uruguay to prevent the move.
Venezuela's Information Ministry, which handles all media inquiries, did not immediately respond to a request to comment.
Russian Federation and China, who have poured billions of dollars of investment and loans into Venezuela, are supporting Mr Maduro in an extension of their geopolitical tussle with the United States.
Earlier this month, Wood Mackenzie analyst Ann-Louise Hittle warned that Venezuela's crude oil production could fall below 1 million bpd after the United States imposed new sanctions on struggling oil firm PDVSA. Fears of U.S. military intervention were raised when U.S. National Security Advisor John Bolton was photographed at a press briefing holding a legal pad with the note "5,000 troops to Colombia" written on it. Bolton later told the press that "all options are on the table" but denied any military action was being planned.