Venezuelan opposition leader Leopoldo Lopez said president Nicolas Maduro's generals are willing to defect from his regime imminently, as Spain vowed to protect the politician.
Speaking from the gates of the Spanish ambassador's residence in Caracas, the Venezuelan capital, on Friday Mr Lopez said: "It's a crack that will become a bigger crack... that will end up breaking the dam".
Mr Lopez said he had spoken with senior members of the military who supported the end of Mr Maduro's socialist government amid a failing economy and nationwide blackouts.
Spain has refused to hand Mr Lopez, a leading figure in the country's opposition movement, over to Venezuelan authorities, saying "Spain trusts that the Venezuelan authorities will respect the inviolability of the Spanish Ambassador's residence."
The politician had been under house arrest for months but escaped to appear alongside his successor in the movement, Juan Guaido, on Tuesday as they called for a military uprising aimed at toppling Mr Maduro.
He later sought refuge in the Spanish embassy after the uprising stalled and a court issued a warrant for his arrest.
Mr Lopez claimed he had met with generals who were committed to ending Mr Maduro's "usurpation" and helped him escape his house arrest.
"I had meetings in my house when I was under house arrest. I met there with commanders, I met there with generals. I met there with representatives of specific parts of the armed forces and specific parts of the police forces," he said.
He added that he believed Mr Maduro's government would fall "in weeks."
That brought a rebuke from Venezuela's ambassador in Madrid Mario Isea, who accused Mr Lopez of using "the ambassador's residence as an operational base to abet a military uprising".
Spain's acting foreign minister Josep Borrell later warned Mr Lopez not to turn the embassy into "a centre of political activism."
After a week of growing tensions Donald Trump, the US president, and his Russian counterpart Vladimir Putin talked for more than an hour on Friday during which time they discussed Venezuela.
Mr Trump said he stands by the Venezuelan people and urged a peaceful solution to the crisis during the phone call with Mr Putin.
The two leaders also talked about a new arms control treaty, North Korea and briefly discussed special counsel Robert Mueller's report into Russian election meddling.
Mr Trump's national security team and the commander of US Southern Command said they held a meeting at the Pentagon to review and refine military planning and various options for responding to the crisis in Venezuela.
The ongoing unrest claimed a fifth fatality on Friday when 15-year-old boy was killed during a protest in the northwestern state of Merida.
The non-government Venezuelan Observatory of Social Conflict said Yonder Villasmil was killed during a demonstration over power outages on Thursday night.
More than 200 people have been injured in clashes rocking the nation this week after Mr Guaido, called for protests to spark a military uprising.
Mr Guaido has called for a return to the streets on Saturday morning, saying at a press conference that Venezuelans should try talking to soldiers directly and telling them to "join the movement."