Buoyed by the defection of a top general, Venezuelan opposition leader Juan Guaido predicted on Saturday the month of February would be "decisive" in determining the future of the nation as he and socialist leader Nicolas Maduro held competing mass rallies in the capital.

National Assembly head Guaido, 35, had called Saturday's protest to ramp up the pressure on Maduro to step down, 10 days after stunning the world by declaring himself "interim president" of the oil-rich but crisis-wracked country.

He received a boost before it began when an air force general became the highest ranking officer to abandon Maduro and recognise the Guaido as the country's true leader.

US National Security Advisor John Bolton responded to that in a tweet calling on "all military members to follow General (Francisco) Yanez's lead".

The US recognised Guaido as Venezuela's interim president on January 23 while four major European nations - Britain, France, Germany and Spain - have said they will do likewise unless Maduro calls presidential elections by 00:00 on Sunday.

Legislative elections

Speaking at a pro-regime demonstration marking 20 years since his predecessor Hugo Chavez came to power, Maduro ignored those demands and instead reiterated his call to bring forward legislative elections slated for the end of 2020 to this year.

"They [the opposition] want to bring forward elections, let's have elections," he said in a reference to the opposition.

Maduro, making his first public appearance since claiming to have survived an assassination attempt six months ago, accused Guaido of being a US "puppet" in a coup d'état attempt.

The National Assembly is the only one of Venezuela's five government branches controlled by the opposition.

Guaido had earlier urged the armed forces to allow into the country humanitarian aid from abroad.

"You, soldier... have the decision in your hands" to allow it in or not, said Guaido.

Under Maduro's stewardship, oil-dependent Venezuela has lurched into an economic crisis that has left the country with hyperinflation and shortages of food and medicine.

Maduro refuses to let aid into the country, claiming it would precede a US-led military intervention.

Guaido called for a new demonstration on February 12 and said there would be yet another one related to the humanitarian aid.

Speaking at the European Union's headquarters in the east of the capital, he said this month "should be decisive".

The rival Caracas rallies, separated by 10km, attracted huge crowds.

Carlos Morales, a 62-year-old who voted for Chavez in 1998 but now says socialism only brings "misery", attended a pro-Guaido rally with his wife.

"This is the leader that all Venezuelans hoped for, a new leader, young, who is not contaminated," he added.

At the pro-Maduro demonstration, Virginia Rondon, 69, hummed songs that glorified Chavez, and reminisced about his socialist revolution, saying: "I never experienced anything more beautiful in all my years."

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