The United States on Wednesday accused its adversaries Venezuela and Cuba of fomenting strife in South America, where a number of countries have seen major protests.

Elliott Abrams, who leads the US effort to topple Venezuela's leftist leader Nicolas Maduro, said the two governments have used social media and other means to stir up unrest.

"There is evidence beginning to build about an effort by the regimes in Cuba and Venezuela to exacerbate the problems in South America," he told reporters.

Abrams pointed to US ally Colombia's recent expulsion of 59 Venezuelans for taking part in mass demonstrations against the unpopular conservative president, Ivan Duque.

Secretary of State Mike Pompeo spoke Wednesday by telephone with Duque and welcomed the "national conversation" he has initiated to discuss grievances.

"Secretary Pompeo reaffirmed the United States' steadfast support for the government of Colombia in its efforts to facilitate peaceful democratic expression," a State Department statement said.

US officials have previously also alleged Venezuelan involvement in demonstrations that have rocked Ecuador and Chile.

Despite the turbulence in the region, Maduro remains in power even though most Western and Latin American nations consider him illegitimate after widespread reports of irregularities in elections last year.

Maduro enjoys support from China and Russia, which in turn accuses the United States of trying to carry out a coup in Venezuela.

The United States in January launched a campaign of sanctions and other pressure to topple Maduro and back Juan Guaido, the head of the opposition-led National Assembly whom Washington considers interim president.

Abrams said the United States would not change course and still expected success.

"No, we don't have a Plan B. We have a Plan A. We think it will work," he said.

"There can be no solution to the terrible problems faced daily by Venezuelans while the Maduro regime is in power, because the Maduro regime created those problems and is exacerbating them," he said.

Maduro presides over a crumbling, state-directed economy that has seen eye-popping levels of inflation and triggered the exodus of millions of Venezuelans who cannot find basic necessities.