An American oil executive freed from custody in Venezuela said that even as he celebrates with his family the end of a long “nightmare,” he’s praying for the release of five colleagues who are still imprisoned and “deserve the same blessings.”

Gustavo Cardenas arrived to his home in Houston at 4 a.m. Wednesday after flying overnight from Caracas with a senior State Department official sent to negotiate the release of American prisoners in the South American country.

In a statement to The Associated Press, he said his imprisonment of more than four years “has caused a lot of suffering and pain, much more than I can explain with my words.”

“I got out of jail and got my freedom after about 1,570 days of wrongful captivity. It was a very hard time marked by deep pain, but also by faith, hope, love and survival,” he said.

He called for the prompt release of the remaining members of the Citgo 6 — for the Houston oil company where they all worked. “They and their families deserve the same blessings and freedom that I got last night,” he said.

He credited his release to President Joe Biden and other U.S. officials as well as the support received from former New Mexico Gov. Bill Richardson and Mickey Bergman of the Richardson Center, which has worked to secure the release of dozens of Americans detained abroad.

Notably absent was any mention of Venezuelan President Nicolás Maduro, whose government jailed the men when they traveled on a corporate jet to Caracas around Thanksgiving 2017 for what they thought was an emergency meeting with Citgo’s parent company, state run oil giant PDVSA.

Instead, masked security forces bearing assault rifles busted into a conference room and arrested the men. Later they were sentenced on charges stemming from a never-executed plan to refinance some $4 billion in Citgo bonds by offering a 50% stake in the company as collateral. Prosecutors accused the men of maneuvering to benefit from the proposed deal.

They’ve always maintained their innocence even as the U.S. has accused Maduro of using them a political bargaining chips to extract concessions from the U.S.

The release of Cardenas and Jorge Fernández, an American imprisoned in Venezuela who was not a member of the Citgo 6, came hours after Maduro signaled an interest in improving relations with the U.S. at a time when Russia’s invasion of Ukraine has sparked concerns in the United States over rising gas prices. In a televised address, he indicated he would accede to U.S. demands that he resume negotiations with his opponents as a first building block for any relief from U.S. sanctions that have been punishing the OPEC nation for years.

U.S. officials have not detailed any other specific outcomes of the talks, but said the release reflected months of relationship-building, particularly involving Roger Carstens, the administration’s special presidential envoy for hostage affairs who accompanied Cardenas and Fernandez back to the U.S.

Carstens made a trip to Venezuela in December that did not immediately result in the release of detainees but that senior administration officials credited with establishing trust and laying the groundwork for Tuesday’s outcome. He returned to Venezuela last weekend with other administration officials including Juan Gonzalez, the National Security Council director for the Western Hemisphere, and Ambassador James Story, who heads the U.S. government’s Venezuelan Affairs Unit out of neighboring Colombia.

The Biden administration described it as the first Venezuela visit by a White House official since Hugo Chávez led the country in the late 1990s, and a rare opportunity to discuss policy issues with the Maduro government. One official described it as “a constructive, diplomatic but very candid dialogue” that did not entail any quid-pro-quo but allowed the Biden administration to share its “view of the world” with Maduro.

Besides the other members of the Citgo 6, several other Americans remain held in Venezuela. Two former Green Berets, Luke Denman and Airan Berry, were arrested for their involvement in a confusing plot to overthrow Maduro, and former U.S. Marine Matthew Heath was detained on weapons charges.

Fernandez was detained in February 2021 near the border with Colombia after he was found in possession of a drone, whose use is restricted in Venezuela. He was accused of terrorism.

The weekend discussions came a little more than three years after the U.S. broke off relations with Maduro and recognized opposition leader Juan Guaidó as Venezuela’s legitimate leader.

The talks came together after months of backchannel efforts by intermediaries — American lobbyists, Norwegian diplomats and international oil executives — who have been pushing for Biden to revisit the so far unsuccessful “maximum pressure” campaign to unseat Maduro that he inherited from the Trump administration.

But the impetus for the outreach to Maduro, who has been sanctioned and is indicted in New York on drug trafficking charges, took on added urgency following Russia’s invasion of Ukraine and ensuing U.S. sanctions. The Ukraine crisis promises to reshuffle global alliances and add to rising gas prices driving inflation already at a four-decade high.

Powerful Democrats and Republicans alike on Capitol Hill last week began voicing support for a U.S. ban on Russian oil and natural gas imports as the next step to punish Russian President Vladimir Putin for the invasion.

Venezuela is Putin’s top ally in Latin America and a top oil exporter. Its reentry into U.S. energy markets could mitigate the fallout at the pump from a possible oil embargo on Russia. But the discussions in Caracas were quickly condemned by top Democrat and Republic senators.

U.S. Sen. Bob Menendez, the Democratic chairman of the Senate Foreign Relations Committee, said Biden’s efforts to unite the world against Putin “should not be undercut by propping up” Maduro, whose government is under investigation by the International Criminal Court for possible crimes against humanity committed against protesters in 2017.

The U.S.-backed faction of the opposition on Wednesday insisted that it remains open to resuming negotiations with Maduro with the goal of scheduling free and fair presidential and congressional elections and said any easing of economic sanctions must be accompanied by advances toward democracy.

“The lifting of any measure of pressure, if it is not oriented toward democratization, would only strengthen the authoritarianism that threatens the world today,” the group said in a statement. “… Only a Venezuela with democratic, institutional and transparency guarantees can be a reliable and efficient energy provider for the world.”