The UN Security Council on Thursday unanimously backed ECOWAS efforts to ensure Gambia's leader Yahya Jammeh hands over power as the West African bloc amassed a military force ready to intervene.
A resolution drafted by Senegal won the support of all 15 council members including Russia, which stressed that the measure did not formally authorize military action in The Gambia. Senegalese troops crossed the border shortly after the UN's endorsement.
The Economic Community Of West African States has repeatedly called on Jammeh to accept his defeat in the December 1 election and step down after 22 years in power.
The resolution calls on the council to give "its full support to the ECOWAS in its commitment to ensure, by political means first, the respect of the will of the people."
The measure does not, however, invoke Chapter 7 of the UN charter, which authorizes the use of force.
Hours earlier, Adama Barrow was sworn in as president at the Gambian embassy in Dakar and immediately demanded loyalty from the defense and security forces.
Russian Deputy Ambassador Petr Iliichev stressed that the resolution calls for political means to resolve the standoff and warned that military action could fail.
"For the time being, there is no bloodletting but if they intervene, who is going to take responsibility for that?" Iliichev told reporters ahead of the vote.
Nigeria and Ghana were sending troops and air power to Senegal to join a Dakar-led regional force preparing to carry out a military intervention in The Gambia.
UN diplomats said that if Barrow requests a military intervention in The Gambia, this would provide the legal basis for the use of force.
"We are hoping that there is a peaceful resolution to this, but it is very clear that if President Barrow asks for assistance, then that is something that, as the legitimate president of Gambia, he is perfectly entitled to do," said British Deputy Ambassador Peter Wilson.
The resolution requests that Jammeh "carry out a peaceful and orderly transition process, and to transfer power" to Barrow.
It urges "all stakeholders, within and outside The Gambia ... exercise restraint, respect the rule of law and ensure the peaceful transfer of power."