South Sudan rebel chief Riek Machar will miss an international deadline on Saturday to return to the capital to take up the post of vice president, the government and rebels said, with his arrival now expected next week.

"There is no coming today," Minister of Information Michael Makuei said, adding that the government will issue flight clearance for Machar to arrive by airplane from Ethiopia only after international monitors have verified the number of weapons carried by the rebels accompanying him.

The rebels, who were at an airport in Ethiopia, said they were ready to fly but needed permission to do so.