JUBA, South Sudan (AP) — South Sudan's opposition is calling for a six-month extension to implement next steps in a fragile peace deal as a major deadline approaches next month to form a power-sharing government between the president and his longtime rival.

Opposition deputy chairman Henry Odwar tells The Associated Press that the extension is needed because security arrangements are not yet adequate.

South Sudan's government rejects the idea of an extension, further raising concerns among observers that the peace agreement signed in September could fall apart.

The deal ended five years of civil war that killed nearly 400,000 people and sent millions fleeing.

May 12 is the deadline for opposition leader Riek Machar to return and once again serve as President Salva Kiir's deputy, an arrangement that more than once has ended in gunfire.