South Sudan's government is making its first public response to a rebel leader's call for a return to armed conflict, saying Riek Machar is placing his own ambition above peace.

In the statement released Wednesday, Machar's replacement as vice president, Taban Deng, says the call to arms is "unacceptable."

Machar fled South Sudan when fighting erupted in the capital, Juba, in July. President Salva Kiir quickly replaced him as vice president in a unity government under a fragile peace deal.

Machar is now in neighboring Sudan. He made his call to rebellion over the weekend.

Government spokesman Ateny Wek Ateny in the statement accuses Machar's forces of attempting "a coup" in July.

South Sudan's civil war began in December 2013 and has killed tens of thousands of people.