The Gambia's top brass have flip-flopped over whether they will remain loyal to Jammeh.
PIC: Jammeh initially conceded defeat on state television, before U-turning his position days later. (AFP)
Gambian President Yahya Jammeh will effectively become a "rebel leader" if he fails to leave office at the end of his mandate in January, the nation's government-in-waiting said Sunday.
Halifa Sallah, a spokesman for the opposition coalition that spurred president-elect Adama Barrow to victory over Jammeh in a December 1 poll, said the longtime leader had no constitutional mandate to remain in office beyond January.
"Any president who loses constitutional legitimacy becomes a rebel," Sallah said.
"Anybody who is a military officer or civil servant who refuses to be under another constitutional authority obviously would also become a rebel," he added.
The Gambia's top brass have flip-flopped over whether they will remain loyal to Jammeh, drawing warnings from the international community.
West African presidents, meanwhile, called on Gambian security forces to act in the national interest and "protect lives and property" in a statement issued after talks among the regional ECOWAS bloc on Saturday.
Sallah read an address to the nation on Barrow's behalf that made clear the president-elect intended to take power in January once Jammeh's five-year mandate expired.
"The constitution orders that I assume office on the day the term of office of outgoing President Jammeh expires. He assumed office on 19th January 2012. His term expires in January 2017," Barrow said in the statement.
"On the day his term expires my term as the lawful President of The Gambia begins," he added.
The west African leaders attending Saturday's summit will attend Barrow's inauguration, they said, and would "take all necessary actions to enforce the results".
"Head of States will attend the inauguration of the President-elect Adama Barrow who must be sworn in on 19th January 2017 in conformity with the Gambian constitution," an ECOWAS statement said.
The group called on Jammeh to accept the result of the result and "refrain from any action likely to compromise the transition and peaceful transfer of power".
This followed talks held by four west African heads of state dispatched to Banjul on Tuesday that failed to yield a deal with Jammeh to cede power.
Meanwhile a planned transition with Jammeh's involvement looks near impossible.
Jammeh initially conceded defeat after 22 years in power on state television, in a segment broadcast on December 2.
One week later, following a recount of the results that still gave Barrow a narrow win, Jammeh said he was voiding the election.
Since then his Alliance for Patriotic Reorientation and Construction party has lodged a controversial complaint with the Supreme Court seeking to overturn the result.
An avalanche of international condemnation has followed, along with reports that Barrow is fearing for his safety with no state protection.