A South Sudanese activist living in exile in the United States has been sentenced to nearly four years in prison for attempting to traffic military-grade weapons to his country in order to carry out a coup, US authorities announced.

Peter Biar Ajak, a government critic and Harvard-educated economist who has worked for the World Bank, was arrested in March 2024 along with Abraham Chol Keech, a South Sudanese national who had become a US citizen.

Ajak had lived in the United States since 2020, having sought asylum after accusing South Sudanese President Salva Kiir of trying to have him killed.

Both defendants pleaded guilty to violating laws controlling the export of arms and military equipment, the US Department of Justice said in a statement Friday.

A federal court in Arizona sentenced Ajak to 46 months in prison. Keech was sentenced in December to 41 months in prison.

‘Install himself’

"From a suburb of our nation's capital, Ajak conspired to export US weaponry to South Sudan, where he planned to lead a coup and install himself in power," said Assistant Attorney General for National Security John Eisenberg.

Between February 2023 and February 2024, the two men "amassed a $4-million arsenal of military-grade weapons," including Stinger missiles, grenade launchers and more than a thousand machine guns and rifles, the statement said.

They were arrested after a year of negotiations with people they believed to be potential suppliers, but who were in fact undercover US federal agents.

Ajak, a prominent South Sudanese activist, had been arrested in his home country in July 2018 for calling on Kiir and opposition leader Riek Machar to step down and make way for new leaders, after a civil war that left 400,000 people dead.

Sentenced to two years in prison for "espionage," he was pardoned in January 2020 by Kiir.