The United States on Wednesday imposed sanctions on South Sudan's first vice president Taban Deng Gai, the U.S. Treasury Department said in a statement.

The move is the latest by the U.S. to pile more pressure on the country's feuding factions to form a unity government aimed at restoring peace in the country.

Gai, former governor of an oil-rich region in South Sudan, has long been a powerful government figure in the country with close ties to President Salva Kiir.

In a statement, U.S. Secretary of State Mike Pompeo urged the government and opposition to distance themselves from impeders of the peace process. He said Gai, on behalf of Kiir, acted to "divide and sow distrust, extend the conflict in South Sudan, and impede the reconciliation and peace process."

"Disappearances and extrajudicial killings of political opposition and civil society actors whose views differ with the ruling regime are actions designed to silence dissent and enforce the political status quo.  Such human rights violations and abuses curtail the political space needed for the full implementation of a durable peace in South Sudan." the statement added.

Gai could not immediately be reached for comment.

South Sudan has been dogged by a conflict since December 2013, sparked by a feud between President Kiir and Riek Machar, his then deputy.

Kiir accused Machar of plotting a coup against his rule, allegations the latter denied but then went on to mobilize a rebel force to fight the government.

Regional and international players hope the formation of a transitional unity government will put the country on the path to lasting peace, with democratic elections slated for further ahead.