Eleven European Union finance ministers are meeting with the aim of reaching agreement on the basic principles of a uniform tax on financial transactions.
However, officials said there were still outstanding differences going into the meeting.
Talks on a financial transaction tax have dragged on since 2011.
In September this year, the ministers from Germany, France, Italy, Austria, Belgium, Estonia, Greece, Portugal, Slovakia, Slovenia and Spain said they had made progress and that they expected a political deal in December.
But some officials were sceptical, saying differences remained large on how to levy the tax, on which financial products, and at what rate.
"We already had so many meetings and somehow it always failed because of one of the member states or on technical issues," German Finance Minister Wolfgang Schaeuble told reporters on entering the meeting.
"I don't know what else I should do. We have to agree, and if not today, than we have to try it again next year."
Germany and France proposed the financial transaction tax at the height of the euro zone debt crisis as a political symbol to recover some of the public money used to support banks, curb speculative trading and unify similar levies already charged in several EU countries.
But talks collapsed in 2012 in the face of stern opposition from Britain and Sweden.
A smaller group of 11 EU countries decided to push ahead with the idea and negotiations have been going on since then.
