Since his reappointment, Bainimarama has imposed emergency restrictions and refused to hold elections before 2014.
After a briefing from Lynn Pascoe, the UN political department chief, the security council said it was "deeply concerned about the situation in Fiji, where undemocratic decisions were made, including the abrogation of the constitution".
Pascoe said that preparations that had been under way for the United Nations and the Commonwealth to mediate dialogue in Fiji faced suspension "unless there is a change in the current state of affairs".
Senior lawyer reinstated
However, the council's 15 members "expressed hopes that Fiji would make a steadfast advancement toward democracy and that free elections will be held at the soonest possible time".
Meanwhile, the former solicitor-general of Fiji, who was recently dismissed amid the political upheaval, has accepted reappointment, saying that the country needs qualified lawyers to help restore the rule of law.
Christopher Pryde, a former New Zealand lawyer, has rejected calls by the New Zealand and Fiji law societies for lawyers to refuse appointments to posts in a military government that has been found unlawful.
Pryde said on Tuesday that "it is vitally important at this time in Fiji's history that people assist the country in getting back on its feet".