Security forces look on while clashing with opposition supporters participating in a rally against Venezuelan President Nicolas Maduro's government and to commemorate the 61st anniversary of the end of the dictatorship of Marcos Perez Jimenez in Tachira, Venezuela, Jan. 23, 2019.

One of the two anonymous Russian sources, who is close to the Wagner group and fought in foreign conflicts where it was active, said the contractors first arrived in advance of the May 2018 presidential election, but another group arrived "recently".

"I am the only president of Venezuela", Maduro was quoted by The Associated Press as saying.

"President Trump has made no secret of the fact that he is not a fan of American deployments all over the world and American entanglements", Pence told Trish Regan Primetime.

On Wednesday, President Donald Trump joined the leaders of several other countries in recognizing Guaido, the president of Venezuela's national assembly, as president of the country.

In Pence's second call, which according to a White House official was kept under wraps for security reasons, the vice president assured Guaido: "We're praying for you, the USA stands with you, your bravery and courage are something we admire".

Juan Guaido has the support of a lot of the population but even with this support he can't really make Maduro quit. Their departure came after Maduro broke off relations with Washington and ordered the USA personnel out.

From then on, countries in the region realized they had a partner in the US willing to tackle a crisis that had been years in the making but which previous USA administrations had chosen to play down because of limited national security implications, said Fernando Cutz, a former senior national security adviser on Latin America to both President Barack Obama and Trump.

But Guaido tweeted in response that, under him, Venezuela wants countries "to maintain their diplomatic presence in our country".

Although it stopped short of following Washington and recognizing Guaido as interim president, it appealed for him to be protected and appeared to support calls for a peaceful transition of power away from Maduro.

Pompeo says the USA doesn't recognize the authority of Maduro and that he doesn't have the legal authority to break diplomatic relations with the U.S.

"Venezuela is not alone!" he added.

Colombian President Ivan Duque, another U.S. ally also at Davos, told reporters his country was behind Guaido and will "accompany this process of transition to democracy so that the Venezuelan people free themselves of their dictatorship".

"Almost certainly the administration is going to have to find a way to get most of our people out of there, and leave behind some kind of symbolic presence to show that we did not leave", the former official said.

Meanwhile, pressure on Venezuela is still mounting.

Eleven members of the 14-nation Lima Group - Argentina, Brazil, Canada, Chile, Colombia, Costa Rica, Guatemala, Honduras, Panama, Paraguay and Peru - later issued a joint statement endorsing Guaido as interim president.

The most notable holdout is Mexico, whose new leftist president, Andres Manuel Lopez Obrador, has pledged a foreign policy of non-intervention. "He's long understood that the United States has a special responsibility to support and nurture democracy and freedom in this hemisphere and that's a longstanding tradition".