"Today the consultation process began...to declare a state of emergency in accordance with the constitution and protect our people, our peace, and our stability if Venezuela were attacked by the American empire, attacked militarily," Maduro said in a televised address.

Earlier in the day, Vice President Delcy Rodriguez told foreign diplomats that Maduro had signed a decree giving himself "special powers" as head of state to act in matters of defense and security in the event the United States "dares to attack our homeland."

A government source, however, told AFP that Maduro had not yet signed the document.

"The vice president presented the document to show that everything was ready and that the president can decree it at any time," the source said, speaking on condition of anonymity.

The left-wing authoritarian Maduro placed Venezuela on high alert over a major US military deployment near his country's coast.

US President Donald Trump has deployed eight warships and a nuclear-powered submarine to the southern Caribbean as part of a stated plan to combat drug trafficking, but which appears particularly aimed at pressuring Maduro.

US forces have destroyed at least three suspected drug boats in the Caribbean in recent weeks, killing 14 people in a move decried as "extrajudicial execution" by UN experts.

Now, US military officials are drawing up options to target drug traffickers inside Venezuela's borders, according to a report by US news outlet NBC, citing four sources familiar with the discussions.

Declaring a state of emergency would allow Maduro, whose disputed reelection last year was not recognized by much of the international community, to temporarily suspend Venezuelans' basic rights.

Rodriguez was confident that Venezuelans would unite behind Maduro in the event of a US attack.

"Venezuela is united in the defense of our country," she said, vowing: "We will never surrender our homeland."

In his address, Maduro also asserted that he had "good feedback" from a private conversation he'd had with UN Secretary-General Antonio Guterres.

Maduro said that Guterres had expressed his "astonishment at an unprecedented escalation, an extravagant escalation, which, for almost seven weeks, was announced and launched against a peaceful country, Venezuela."

These assertions have not been confirmed by the UN.