Former US ambassador Bill Richardson will meet Venezuelan President Nicolas Maduro to seek the release of prisoners, his office said Monday, a sharp contrast to the administration's shunning of the leftist leader.

Richardson, "at the request of several American prisoners' families, is traveling to Caracas on a private humanitarian mission," the former Democratic politician's office said.

He will "meet with Venezuelan President Nicolas Maduro to discuss the status of the American prisoners and other COVID-19 humanitarian issues," the Richardson Center said on Twitter.

Richardson, a former US ambassador to the United Nations and governor of New Mexico who speaks Spanish fluently, has frequently embarked on missions to help US prisoners, often to the unease of hawks in President Donald Trump's administration.

The United States no longer recognizes Maduro as Venezuela's president and has been trying unsuccessfully since early 2019 to oust the leftist leader, who presides over a crumbling economy that has caused millions to flee.

Former New Mexico governor Bill Richardson, seen here in 2014, plans to meet Venezuelan President Nicolas Mdauro to seek the release of US prisoners Former New Mexico governor Bill Richardson, seen here in 2014, plans to meet Venezuelan President Nicolas Mdauro to seek the release of US prisoners Photo: GETTY IMAGES NORTH AMERICA / Alberto E. Rodriguez

The administration has previously said that it will only speak to Maduro and his entourage about leaving power or about logistical issues, such as the status of the US embassy.

The State Department has voiced growing concern over the safety of six former executives from the oil company Citgo -- five of them dual US-Venezuelan nationals and one a US resident.

They were first arrested in November 2017 and accused of crimes including money laundering. Their families scoff at the charges, saying that Maduro controls the judiciary and is notorious for corruption.

Roger Carstens, the US envoy for hostage affairs, said last month that all six men were "in mortal danger," with several displaying symptoms in line with COVID-19.

Venezuela's foreign minister, Jorge Arreaza, countered that the authorities had respected their rights and accused the State Department of lying.

Richardson said last month that he had met Iranian Foreign Minister Mohammad Javad Zarif, also shunned by the Trump administration, to seek the release of an American who was later freed to a State Department official.