Lieutenant General Ousman Badjie used a New Year message published in the pro-government Daily Observer newspaper to "renew to Your Excellency (Jammeh) the assurance of the unflinching loyalty and support of The Gambia Armed Forces".
Regional leaders warned last month that the 15-member Economic Community Of West African States (ECOWAS) would "take all necessary action" to enforce the results of a disputed December 1 poll that Jammeh lost to Adama Barrow.
Top ECOWAS official Marcel Alain de Souza described force as a "possible solution" if Jammeh clings to power, while Senegalese President Macky Sall, whose nation almost entirely surrounds The Gambia, said a military intervention could be the final course of action.
Jammeh, who has been in power for 22 years, stunned observers by initially accepting his defeat, but then made a U-turn a week later, rejecting the results and then filing a court challenge against the Independent Electoral Commission (IEC).
Diplomats in the region have voiced private concern that Barrow's safety is not being guaranteed by the state, as he relies on unarmed volunteers to act as bodyguards.
Barrow initially claimed the army chief had personally assured him of his support, but Badjie subsequently appeared at high-level mediation talks in Banjul in mid-December saying the incumbent was still his boss.
A crackdown in recent days by security agents has also shut two radio stations, while a group of traders selling t-shirts featuring Barrow's image were briefly detained.
Hannah Forster, executive director of the Gambia-based African Centre for Democracy and Human Rights Studies, described the media repression as "a blow to democracy" on Wednesday.
"These radio stations have been sharing information in the local languages...I would like the government to reconsider their decision," she told AFP.
On Tuesday evening Jammeh and his party filed two more legal complaints with the Supreme Court, claiming two regions had their results doctored and alleging Jammeh was denied a "well-earned victory".
"If the result was properly collated, the outcome would have shown that the Petitioner (Jammeh) won the election," said a court filing lodged by Jammeh himself and seen by AFP Wednesday.
Meanwhile 20,000 Jammeh supporters in these regions were "dissuaded by IEC officials from voting," the filing said, calling for a re-run in the areas affected.
The head of Gambia's electoral commission has fled to neighbouring Senegal fearing for his safety, meaning he is unlikely to appear in any of the three court cases now lodged against him.
Alieu Momar Njie suspected a plot against him after his commission's headquarters were locked down by the security forces for several days while Jammeh challenges the election result in the Supreme Court.
The second complaint lodged by Jammeh's campaign chief Yankuba Colley on Tuesday said it represented 5,300 voters denied the right to cast their ballots.
If they had been permitted to vote it "would have altered the result of the election," according to the document.
The election was hailed internationally as free and fair, but Jammeh has cited a recount issued in the days after the election as evidence of manipulation by the IEC.