Guaido, who is recognized by more than 50 countries including the United States and Brazil, has called protests for the May 1 workers' holiday that he has vowed will be "the biggest in the history" of Venezuela.

"We are keeping up diplomatic pressure to support the mobilization -- the very intense popular mobilization -- of Juan Guaido, with great expectations for May 1," Foreign Minister Ernesto Araujo told reporters after talks in Washington with Secretary of State Mike Pompeo.

He renewed calls for the military -- whose leadership has stood behind leftist President Nicolas Maduro -- to switch sides and back Guaido.

"We expect Venezuelan troops to patriotically show their support for the legitimate government. If they do so, it would be fantastic," he said.

Araujo nonetheless called for "caution" on predicting events in Venezuela, where Maduro has held on to power despite escalating pressure in the three months since Western and Latin American powers declared him illegitimate.

Pompeo, asked separately at an event of The Hill newspaper if Maduro would fall this year, said: "I don't do timelines."

"The opportunities in South America are enormous. We've seen this shift to freer economies, more democratically elected leaders, and if we can get Venezuela to go right... there will be enormous economic growth," Pompeo said.

The change in power will benefit not only "people in those countries, but the United States as well," he said.

Brazil's new far-right president, Jair Bolsonaro, has found common cause with President Donald Trump in their antipathy to leftists in the hemisphere.

Maduro was reelected last year in a vote widely seen as fraudulent, with Guaido's opposition forces in control of the National Assembly.

Venezuela is witnessing a major economic crisis, with inflation projected to hit a mind-boggling 10 million percent this year. Some 2.7 million people have fled since 2015 in the face of shortages of basic goods and medicine, according to UN figures.