Supporters of opposition leader Juan Guaido demonstrated Saturday in Caracas.
CNN  — 

A Venezuelan military helicopter crashed on Saturday in Hatillo, a municipality near Caracas, killing all seven on board, according to a statement released by the Ministry of Defense.

Embattled Venezuelan president Nicolas Maduro acknowledged the lives lost in the crash in a message posted on Twitter, and sent his condolences to the victims’ relatives and friends on Saturday night.

In his tweet, Maduro said the seven who died were officers in the Fuerza Armada Nacional Bolivariana, or National Bolivarian Armed Forces, known by its Spanish initials FANB.

According to the Ministry of Defense, authorities are currently investigating the deadly crash.

Pressure has been mounting on Maduro to step down since January, when opposition leader Juan Guaido declared himself interim president and was backed by the US and dozens of other nations.

Maduro and Guaido are jockeying for the support of the military, which is seen as key to ending the stalemate.

Protesters clashed with security forces Saturday after Guaido called on his supporters to continue demonstrations by marching to military bases. Reuters captured footage of protesters outside military barracks in Caracas presenting a letter from Guaido to the security forces. In the letter, he asked the military to switch sides, saying, “The time to act is now.”

The soldiers, however, set the letter on fire without reading it. Tear gas and smoke bombs were also deployed against the protesters.

As recently as Friday, US President Donald Trump’s security team met at the Pentagon to discuss potential options in dealing with the Venezuelan political crisis, with Secretary of State Mike Pompeo warning Maduro that he “is not someone who can be part of Venezuela’s future.”

In an interview on ABC News’ “This Week,” Pompeo said Maduro’s regime is being propped up by Cuba, and that “without the Cubans, there’d be no possibility he was still in power.”

Guaido's call for marches to military bases was part of a bid to lure security forces to his side.

While Maduro is struggling to hold onto power, it is anything but clear when or if he might step down.

Pressed on whether Maduro’s exit is imminent, Pompeo demurred, saying, “Could be two weeks, could be four weeks.”

Russian Foreign Minister Sergey Lavrov was meeting Sunday with his Venezuelan counterpart, Jorge Arreaza.

The support of the military is critical to determining the country’s future. A leading Venezuelan opposition figure has claimed he met high-ranking members of the Venezuelan security services and that senior members of the military supported the end of the Maduro regime.

Speaking to journalists at the gates of the Spanish ambassador’s residence in Caracas, Leopoldo Lopez said he met the security officials while under house arrest.

Guaido, however, admitted last week that not enough of the security forces have defected to his side to help in efforts to oust Maduro.

CORRECTION: An earlier version of this story incorrectly described how Juan Guaido came to be Venezuela’s self-declared president.

CNN’s Ryan Browne, Claudia Dominguez, Sandra Sanchez and Natalie Gallón contributed to this report.