A group of senior U.S. officials flew to Venezuela on Saturday for a meeting with President Nicolás Maduro’s government to discuss the possibility of easing sanctions on Venezuelan oil exports as the Biden administration weighs a ban on imports of Russian oil and gas, according to two people familiar with the situation.

The trip is the highest-level U.S. visit to the socialist state in years and comes as the United States is seeking to isolate Russia for its invasion of Ukraine. Venezuela, the Kremlin’s most important ally in South America, used to be a significant supplier of crude to the United States before exports were hobbled by domestic mismanagement and crippling sanctions from Washington.

In recent weeks, former American lawmakers have pushed for the U.S. to ban Russian oil and gas exports while lifting restrictions on Venezuela, home to the world’s largest oil reserves.

The U.S. delegation included Roger Carstens, the special presidential envoy for hostage affairs; Juan Gonzalez, the National Security Council’s senior director for Western Hemisphere affairs; and Jimmy Story, the U.S. ambassador to Venezuela, said one person familiar with the visit.

The trip comes just days after Maduro and Russian President Vladimir Putin spoke over the phone about boosting the partnership between their countries.

The State Department and the White House declined to comment.

During the trip, U.S. officials are also trying to secure the release of six former executives of Houston-based Citgo Petroleum Corp., an oil refiner formerly controlled by the Maduro government, according to a person familiar with the visit who spoke on the condition of anonymity to discuss sensitive diplomatic meetings. The “Citgo 6” were arrested during a business trip to Caracas in November 2017 and charged with money laundering, embezzlement, racketeering and participating in organized crime. They denied the allegations.

The U.S. officials are also seeking to negotiate the release of two former Green Berets who were accused in a plot to remove Maduro, as well as a former marine who was arrested while traveling along the Caribbean coast of Venezuela.

The U.S. and Venezuela broke off diplomatic relations in 2019 after the U.S. government recognized Juan Guaidó as the country’s legitimate president, accusing Maduro of winning reelection through fraud. In an attempt to force Maduro from power, the Trump administration blocked all U.S. revenue to Venezuela’s national oil company.

Biden administration officials have been weighing how to respond to penalize Russia for its invasion of Ukraine without further driving up the cost of oil and of gasoline at the pump.

In recent weeks, some U.S. investors have called on the administration to lift sanctions on Venezuela so it can send more crude oil into the market, the Wall Street Journal reported. Chevron has also lobbied the administration to modify its license to accept and trade oil in Venezuela.

But some Republicans, such as Sen. Marco Rubio (R-Fla.) have sharply criticized the decision by U.S. officials to travel to Venezuela, a trip which was first reported by the New York Times. A decision to re-engage with Venezuela could come at a political cost for the Biden administration and Democrats, particularly in Florida.

“Joe Biden using #Russia as an excuse to do the deal they always wanted to do anyway with the #MaduroRegime,” Rubio tweeted Sunday. “Rather than produce more American oil he wants to replace the oil we buy from one murderous dictator with oil from another murderous dictator.”

Geoff Ramsey, Venezuela director at the Washington Office on Latin America, said the U.S. trip to Caracas comes as negotiators for the Venezuelan opposition have been pushing the Biden administration for “carrots” that could draw Maduro back to talks in Mexico City, which were suspended in October.

“It does seem like there’s a potential for things to shift, I think the question is what the U.S. is going to get in exchange,” Ramsey said. “It’s very unlikely that senior Biden officials would go to Caracas and meet with Maduro and be able to sell a major policy shift like this if they were to come home empty-handed.”

U.S. officials have signaled the Biden administration will continue to recognize Guaidó as Venezuela’s rightful leader. But in an interview with America’s Quarterly this week, Gonzalez said the administration is focused on negotiations, rather than toppling Maduro.

“Whereas the previous administration’s theory of change was based on regime collapse, ours is … that only a negotiation will lead to concrete and sustainable change in Venezuela toward democratic order,” he said.

Opposition leaders reached by The Washington Post said they had no knowledge of the U.S. delegation’s visit, although some of them have been in talks to ease sanctions.

It’s unclear whether Saturday’s talks with Maduro officials will lead to any change in policy. But even if the U.S. were to ease the oil sanctions, Venezuela’s production would do very little to fill the gap left by Russian oil on the world market, said Francisco Monaldi, director of the Latin American Energy Program at Rice University.

While Venezuela has recently increased its oil production slightly, it is only producing about 10 percent of what Russia was exporting, according to Monaldi. “In the short term, Venezuela is irrelevant,” he said.

But if the U.S. stops importing oil from Russia, Venezuelan crude could help fill the gap, he said. When Venezuelan oil was subjected to a U.S. ban, Russian exports took most of Venezuela’s markets in the United States.

“If Venezuelan oil can come back to serve that market, that would be really good for these refiners and might ease their trouble,” Monaldi said. “Having said that, will that significantly reduce what Americans pay at the pump? I doubt it.”