Oil prices rose on Friday after OPEC vowed to eliminate overproduction in order to stick by its output ceiling and boost its members revenue.
The market was also supported by hopes that the US Federal Reserve would step in with new stimulus measures to bolster the world's largest economy, traders said.
New York's main contract, light sweet crude for delivery in July, climbed 57 cents to $84.48 a barrel.
Brent North Sea crude for August delivery gained 41 cents to $97.58 in London midday deals.
"Oil futures rose as the Organization of the Petroleum Exporting Countries agreed to keep its collective oil output ceiling unchanged" at a meeting in Vienna on Thursday, Phillip Futures said in a market commentary.
OPEC decided in the Austrian capital, where the 12 nation cartel is based, to cut total production by 1.6 million barrels per day to meet the group's 30 million mbpd production ceiling agreed last December.
Smaller output could meanwhile give a boost to prices. Brent crude oil has tumbled from $128 a barrel in early March -- mainly on expectations of weaker demand caused by the eurozone's troubles and a slowing Chinese economy.
OPEC Secretary General Abdullah El-Badri said that the world economy would not be threatened by oil prices as high as $110 a barrel, despite fears among consumers that more expensive crude would hinder global economic recovery.
"$110 dollars a barrel is not a threat for world economic growth," El-Badri told journalists in Vienna on Friday.
OPEC, whose members include Saudi Arabia, Iran and Nigeria, pumps out about one third of the world's oil.