The trip, the highest-level US visit to Venezuela in years, came as part of a US effort to isolate Russian President Vladimir Putin. Some analysts also see US-sanctioned Venezuela as a potential alternate source of oil supplies should Washington attempt to restrict Moscow's energy shipments.

US and Venezuelan officials held a round of talks on Saturday but reached no agreement, the source told Reuters on condition of anonymity. It was unclear whether a further meeting would be held.

The visit, which involved senior White House and State Department officials, was first reported by the New York Times.

The White House and State Department did not immediately respond to a request for comment.

The US government has largely shunned direct contacts with Maduro's socialist government in recent years.

The two countries broke off diplomatic relations in 2019 amid a campaign of US sanctions and diplomatic pressure aimed at ousting Maduro, a longtime Putin ally.

Moscow's invasion of the former Soviet republic has pushed the United States to pay closer attention to Russian President Vladimir Putin's allies in Latin America, the paper said, citing anonymous sources familiar with the matter.

Spokesmen for both US President Joe Biden's and Maduro's administrations did not respond to AFP requests for comment.

The United States cut diplomatic ties with Venezuela after Maduro was reelected in 2018 in a vote widely considered fraudulent.

Washington then recognized opposition leader Juan Guaido, then parliament speaker, when he declared himself acting president in January 2019. At least 50 other countries also recognize him.

The United States imposed a battery of sanctions on Caracas in attempts to force Maduro from power.

One measure, implemented in April 2019, prevents Venezuela from trading its crude oil -- which accounted for 96 percent of the country's revenues -- on the US market.

According to the Times, the current visit to Caracas by senior State Department and White House officials is also linked to Washington's alleged interest in replacing part of the oil it currently buys from Russia with the oil it stopped buying from Venezuela.

The White House indicated Friday that it is examining how to reduce Russian oil imports in the wake of the Ukraine invasion without harming US consumers and while maintaining global supply.

The United States signaled last month it would be willing to review sanctions policy toward Venezuela if the talks between Maduro's government and the opposition -- launched in August but suspended since October -- moved forward.