"It must be because investors are looking ahead and seeing that the situation in Europe isn't going to get any better, while the outlook for demand in the U.S. is poor and China is slowing too," Morrison said.

He added that there was little technical support for Brent crude above the $87.50-$88 per barrel level.

Others pointed to ample supply of crude oil in a market where demand growth is slowing.

"The Fed might provide some short term support but there is a fundamental over-supply of light/sweet crude oil in the Atlantic Basin that neither OPEC nor the Fed can resolve," said Olivier Jakob, at Petromatrix in Zug Switzerland.

Traders said they were not focusing on supply disruption risks posed by sanctions on producer Iran over its disputed nuclear programme.

Brent crude ended lower on Tuesday after negotiations in Moscow to defuse the dispute over Iran's nuclear programme led to plans for technical talks to be held in Istanbul on July 3.