Oil prices declined have fallen ahead of a key Organization of the Petroleum Exporting Countries (OPEC) meeting in Vienna to decide production volume.

Brent for July fell 55 cents at $63.25 a barrel, while the US crude futures were 45 cents lower at $59.19, Reuters reported.

At the meeting scheduled on Friday, OPEC countries are expected to maintain the oil production volume of 30 million barrels per day (bpd), which is more than the expected demand, weighing on the prices.

"A rollover in OPEC’s production target is built into prices."

OPEC countries are already producing two million bpd, which is more than needed, adding to the oversupply concerns.

Oil prices are hovering at half the price of the 2014 peak, as there are millions of barrels of oil stored in tankers awaiting buyers.

PVM Oil Associates oil analyst Tamas Varga told the news agency: "A rollover in OPEC’s production target is built into prices."

Energy advisor Wood Mackenzie said OPEC may not agree to cut output and expects Brent to average $60 and $70 a barrel in 2015 and 2016 respectively.

Despite oversupply, an increase in demand for fuel globally has helped support oil prices.

In the first quarter, European diesel demand growth reached 7.2%, or 420,000bpd, compared with the same period last year.

Similar demand is also seen in China as there are two million cars sold in the country despite its economy losing steam.