Venezuela kicks off two days of military drills on Saturday in response to US President Donald Trump's threat of military action and newly announced sanctions on the crisis-stricken nation.
Trump warned on August 11 that the United States was mulling a range of options against Venezuela, "including a possible military option if necessary."
His Vice President Mike Pence later played down the threat, insisting that Washington was prioritizing a diplomatic solution and economic sanctions.
National security advisor HR McMaster followed suit, saying "no military actions are anticipated in the near future."
But tension only surged again when the White House made good on the sanctions threat on Friday, unveiling its first-ever sanctions to target Venezuela as a whole, rather than just Maduro and his inner circle.
The measures ban trade in new bonds issued by the Venezuelan government or its cash-cow oil company, PDVSA.
That could choke off access to New York debt markets and substantially raise the likelihood of Venezuela being forced into default.
Venezuela called the measures the "worst aggression" yet.
"We will protect our people and the people of the republic, the Bolivarian Republic of Venezuela, are going to stand up," said Venezuelan Foreign Minister Jorge Arreaza.
Trump's threat of military force has bolstered Maduro's oft-repeated claim that Washington is plotting to topple him and wants to grab control of Venezuela's oil -- the largest proven reserves in the world.
Maduro is under international pressure over his handling of an economic and political crisis.
The socialist president is resisting opposition calls for early elections to replace him.
The center right-led opposition and international powers including the US say he is turning Venezuela into a dictatorship.
Maduro's opponents accuse military police and pro-Maduro militia of beating and killing anti-government protesters.
Protest clashes have left 125 people dead so far this year, according to prosecutors.
Maduro says the violence and the economic crisis are a US-backed conspiracy.
Maduro, the political heir to the late Hugo Chavez, has managed to hang onto power through it all, despite food shortages and social upheaval.
His grip is largely thanks to the support of the military, which holds vast powers in his government, including over food distribution.
The opposition has repeatedly called on the army to abandon Maduro -- so far to no avail.
He has only faced low-level dissent, such as from the two rebel officers who staged a raid on an army base this month.
On Thursday, the president issued a stern warning to the armed forces not to break ranks.
"We must be clear, especially for the youth in the military, that we must close ranks within the homeland -- that this is no time for any fissures and that those with doubts should leave the armed forces immediately," he said in a speech to the top military brass.
"You are with Trump and the imperialists, or you are with the Bolivarian national armed forces and the homeland," he added. "Never before has Venezuela been threatened in such a way."
Maduro's critics accuse him of coopting the military with top cabinet posts, as well as hijacking state institutions, such as by installing a new constituent assembly packed with loyalists.