Venezuela President Nicolas Maduro on Sunday rejected a European ultimatum that he call elections as opposition rival Juan Guaido stepped up appeals to the military to turn against the leftist government.
The United States, meanwhile, warned there would be a "significant response" if US diplomats, Mr Guaido, or the opposition-controlled National Assembly were targeted with violence and intimidation.
The shot across the bows came after Spain, Britain, France, Netherlands and Germany said on Saturday they would recognise Mr Guaido as interim president unless Mr Maduro calls elections within eight days.
"They should withdraw this ultimatum. No one can give us an ultimatum," Mr Maduro told CNN Turk in an interview dubbed into Turkish from Spanish.
"Venezuela is not tied to Europe. This is complete insolence," Maduro added, as he described the European countries' actions as a "mistake."
Later, he appeared at a military exercise in the state of Carabobo where he called for "union, discipline and cohesion" to defeat what he called an "attempted coup d'etat."
"Traitors never, loyal always," he exhorted the military audience. Televised images showed tanks lined up in a row and soldiers firing their weapons.
"Are you coupsters or are you constitutionalists? Are you pro-imperialist or anti-imperialists," he said.
Thus far, the military has backed the leftist regime, which was ushered into power more than 20 years ago by the late Hugo Chavez, but there have been some signs of unrest.
Pope Francis, winding up a trip to Panama, said on Sunday he was praying that "a just and peaceful solution is reached to overcome the crisis, respecting human rights."
Mr Guaido, the 35-year-old head of the opposition-controlled National Assembly, declared himself acting president at a massive anti-government rally in Caracas on Wednesday, contending that Mr Maduro's reelection to a second six-year term was fraudulent.
His bold bid was swiftly endorsed by the United States, Canada and many Latin American countries.
"Any violence and intimidation against US diplomatic personnel, Venezuela's democratic leader, Juan Guaido, or the National Assembly itself would represent a grave assault on the rule of law and will be met with a significant response," US National Security Advisor John Bolton tweeted on Sunday.
The warning didn't address specific groups or individuals, but Bolton noted in a linked tweet that Cuba's "support and control over Mr Maduro's security and paramilitary forces" was well known.
Mr Maduro has received support from Russia, Syria, Turkey and China as well as longtime allies Cuba and Bolivia.
"All that is happening is linked to America. They are attacking us and they think Venezuela is their back garden," Mr Maduro said in the interview with CNN Turk.
Although he professed himself "open to dialogue," he acknowledged it was unlikely. "I sent many messages to Donald Trump," he said.
In Washington, Republican Senator Marco Rubio, considered a key architect of the US policy on Venezuela, played down the possibility of a military intervention despite his and Mr Trump's warnings earlier in the week that "all options are on the table."
"I don't know of anyone calling for military intervention," Rubio said.
Mr Guaido has aimed his appeals at the Venezuelan military, with promises of amnesty and mass protests to dramatise the depth of popular opposition to Maduro who has presided over a virtual collapse of the economy and a severe humanitarian crisis.
On Sunday, he attended a mass in Caracas in honour of the political prisoners and opposition leaders in exile, as well as the 29 people killed and the more than 350 arrested in clashes with security forces in the past week.
Mr Guaido has asked supporters to circulate copies of amnesty measures approved by the National Assembly to friends and relatives in the military.
Venezuela's military attache in Washington, Army Colonel Jose Luis Silva, switched his support to Mr Guaido in a video that called on his brothers in arms to follow his lead.
At a special UN Security Council session Saturday, US Secretary of State Mike Pompeo described Mr Maduro as part of an "illegitimate mafia state" responsible for Venezuela's economic collapse.
Mr Pompeo urged nations to end financial transactions with Mr Maduro's government, which has struggled to pay bills despite the country's oil wealth.
Russia has denounced the United States for attempting to "orchestrate a coup d'etat," and on Sunday denied reports that 400 members of a private Russian military group were in Venezuela to protect Maduro.
The Venezuelan leader earlier gave US diplomats until late Saturday to leave the country.
But as the deadline expired, Mr Maduro said he had begun negotiations to set up within 30 days an Interests Section in Caracas to maintain a minimum level of diplomatic contact, similar to the arrangement the US had with Cuba until their 2015 rapprochement.
"We have no plans to close the embassy," a State Department official said Sunday. "Our priority remains the safety and protection of our personnel and US citizens overseas.
"Interim President Guaido has invited the US mission to remain in Venezuela. We will continue to evaluate the situation on the ground and determine appropriate action," the official said.