Banjul - West African leaders announced on Monday they would return to Gambia to persuade President Yahya Jammeh to step down, as the strongman was left looking increasingly isolated at home and abroad.The mandate for Jammeh's five-year term runs out on January 18, after which president-elect Adama Barrow is supposed to take power.Nigerian President Muhammadu Buhari would accompany Liberian counterpart Ellen Johnson Sirleaf and Ghana's former president John Dramani Mahama to impress upon Jammeh "the imperative to respect the constitution", Nigeria's foreign minister Geoffrey Onyeama said in Abuja. The same west African leaders at a meeting in Abuja, along with Senegalese President Macky Sall, expressed concern about worsening security, including a crackdown on the media, which has seen a number of radio stations taken off air, Onyeama said.Onyeama said the hope is that a peaceful transfer of power will take place, but that force may be used as a last resort.Imminent defections "Violence should be avoided but nothing is ruled out," he told reporters. The same leaders had made a previous attempt at mediation with both sides of The Gambia's political crisis in mid-December but failed to bring a result.In Banjul, rumours swirled of imminent defections from Jammeh's government, while it was confirmed the leader who has been in power for 22 years had fired The Gambia's ambassadors to 12 different nations, apparently for disloyalty.All the envoys had expressed their support for Barrow in late December, and asked Jammeh to step aside and respect the result of the December 1 election that delivered the opposition leader a narrow victory."I do not know why President Yahya Jammeh terminated their services, but I can tell you that these are the ambassadors that congratulated and endorsed President-elect Adama Barrow for his election victory," a foreign ministry source told AFP on condition of anonymity.Judge shortage? Meanwhile it appeared increasingly clear there would not be the requisite number of judges on Tuesday sitting for Jammeh's Supreme Court case against the Independent Electoral Commission (IEC), seeking to have the election result overturned.Nigerian and Gambian legal experts told AFP that although five Nigerian judges and one from Sierra Leone had been invited to hear the case, none had responded. The Gambia relies on foreign nationals as judges due to a shortage of Gambians with the requisite training and experience.Jammeh and his political party have now lodged three separate legal complaints with the Supreme Court alleging manipulation of ballot counting by the IEC and intimidation of supporters.Gambian legal expert Aziz Bensouda said a quick resolution was unlikely and constitutionally Jammeh still had to step down by the end of his mandate."In the absence of a court and the pure impossibility of the parties being served in time to appear and enter a response, it seems that an adjournment of the case will be the most likely outcome," he told AFP.Jammeh's own lawyer Edward Gomez said he did not know how many judges would appear on the day."Judges have been employed for the Supreme Court, they have been appointed," he told AFP by phone. "Now whether they are here or they are not, I am in no position to tell you."Chief justice Emmanuel Fagbenle is the panel's only sitting judge, as the Supreme Court has lain dormant since May 2015. Several judges were fired after they commuted the death sentences of former military officers to life imprisonment. Radio shutdowns A climate of tension and uncertainty has gripped the Gambian capital in recent days with the closure of several radio stations and arrests of those selling t-shirts sporting Barrow's face.The staff of popular private Gambian radio station Paradise FM, shut down late on Sunday by authorities, told AFP they had lodged a complaint and vowed to keep broadcasting if an explanation was not provided by the information ministry."We told them [the ministry] that we are going to resume broadcasting if we don't hear from them," said Ebou Jaiteh, manager of Paradise FM.