Talks to finalize a cap on the price of Russian oil long in the works by the United States and pro-Ukraine allies faced a setback Wednesday, as a meeting of senior European Union diplomats over the exact price and other details ended without agreement.

The plan is close to being finalized and must be in place before an EU embargo on Russian oil imports kicks in Dec. 5.

EU diplomats from all 27 member states met throughout the day and into the evening Wednesday to iron out the final details, including, crucially, at what price the cap should be set.