Liberia’s President Ellen Johnson Sirleaf will lead a mission to Gambia on Tuesday to mediate in a crisis brought on by long-ruling President Yahya Jammeh’s refusal to step down, president-elect Adama Barrow said.

Jammeh had quickly conceded defeat to Barrow after a presidential election on Dec. 1. But in an about-face on Friday that drew international condemnation, he denounced the results.

He plans to contest the result at the Supreme Court, raising the prospect that a shock opposition victory that was poised to end 22 years of autocratic rule will be overturned.

Barrow told Reuters on Monday that Johnson Sirleaf, a Nobel peace laureate and current chair of the West African regional organisation ECOWAS, would head a delegation representing the bloc as well as the United Nations and the African Union.

Neither the Liberian president’s office nor Gambian officials could be reached for comment.

The mission will meet with both Jammeh and the president-elect and include regional heads of state, Barrow said, though he declined to name which ones.

“With the statement from Jammeh (challenging the poll results) which shocked the world, he made a mistake, and they have to advise him,” Barrow told Reuters at a hotel in the capital Banjul.

Asked what he expected the delegation’s visit to accomplish, Barrow said he wanted to see an “expedited transitional period” that would lead to Jammeh handing over power.

“We are not talking about a military option. We want to safeguard our democracy and we want peace,” he said, but added that he was concerned for his own security.

“I have no official security. As president-elect, I should not be exposed in the way I am today,” he said.

Jammeh seized power in a coup in 1994 when he was an army lieutenant and has ruled ever since, wining four elections that were criticised by rights monitors and surviving several coup attempts. International human rights groups accuse him of widespread violations and repression.

He declared Gambia an Islamic Republic last year.

A statement from the opposition coalition read to reporters in Barrow’s presence on Monday called for Jammeh to step down immediately.

Before his surprise change of mind, he had pledged to hand over power to Barrow in January following the transitional period dictated by Gambian law.

However, Gambia has no sitting Supreme Court. In order to hear Jammeh’s complaint, legal experts believe at least four judges must be hired.

“We do not recognise that the outgoing president has the constitutional authority in the last days of his presidency, to appoint any Supreme Court judges in the Gambia for the purpose of receiving his petition,” opposition figure Mai Fatty said.