Venezuela's self-proclaimed interim president Juan Guaidó has called for mass protests as he announced his return to the crisis-stricken country.
"I call on Venezuelans to gather across the country tomorrow at 11am," he tweeted on Sunday.
Mr Guaidó, who has been recognised by over 50 countries, has called on President Nicolás Maduro to resign.
But Mr Maduro insists he is the legitimate president, and is backed by China, Russia and Cuba.
It is now unclear how he will return to Venezuela, and what action Mr Maduro will take if he does.
The Supreme Court placed a travel ban on Mr Guaidó after he proclaimed his interim presidency.
EU foreign policy chief Federica Mogherini meanwhile said any harm to Mr Guaidó "would represent a major escalation of tensions" and be met with international condemnation.
After crossing the border into Colombia last month Mr Guaidó has toured several Latin American countries, meeting US Vice President Mike Pence in Colombia and Brazil's new President Jair Bolsonaro.
The head of the opposition-led National Assembly declared himself interim president in January in a bid to oust Mr Maduro, who has presided over a growing crisis in Venezuela.
Millions have fled the country, and Mr Guaidó met some of them on Sunday in Ecuador.
Mr Maduro meanwhile has closed borders in an effort to stop humanitarian aid requested by the opposition from entering Venezuela.
At least two people died in clashes between troops and protesters last month.
Venezuela's military strongly backs Mr Maduro, although there are reports of growing numbers of defectors in the ranks.
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