* Brent, U.S. crude still near 2-1/2-week highs
* OPEC needs to pump more in second half of 2014 - IEA
* Libya's El Feel oilfield resumes production
(Updates prices; changes byline, dateline from previous London)
NEW YORK, May 15 (Reuters) - Front-month Brent crude futures held on to gains ahead of the contract expiration on Thursday, while U.S. futures fell even as concerns about the crisis in Ukraine and a tightening global oil market kept prices near 2-1/2-week highs.
News of returning Libya supply provided pressure on oil crude futures, with the OPEC-member country's output at 300,000 barrels per day (bpd) with the El Feel field at full capacity and Wafa field back at work after protests ended in the west of the country, an official with the National Oil Corporation (NOC) said on Thursday.
Expiring Brent crude for June was up 10 cents at $110.29 a barrel by 11:35 a.m. EDT (1535 GMT). Wednesday's close at $110.19 was the highest settlement since April 24.
Brent July was down 22 cents at $109.09 a barrel.
U.S. June crude was down 70 cents at $101.67 a barrel after Wednesday's settlement at $102.37 a barrel, its highest finish since April 21. The U.S. June contract expires on Tuesday.
U.S. RBOB gasoline and heating oil futures also fell on Thursday, pulling back after three consecutive higher settlements.
ENERGY SUPPLY UNCERTAINTY
The exclusion this week of pro-Moscow separatists from talks amongst Ukraine's interim leaders on plans to give the eastern regions greater autonomy cast doubt over moves to defuse the political crisis in Central Europe.
Energy ministers from Russia and the European Union are to meet May 19 to set a date for more talks with Ukraine to end a dispute over gas prices and avoid a potential interruption of energy supplies.
Also highlighting supply worries, OPEC oil producers will need to raise output in the second half of 2014 to meet global demand as China builds its strategic reserves and stocks in industrialized countries remain low, the International Energy Agency (IEA) said on Thursday
"Crude prices remain elevated and forecast balances call for a significant rise in OPEC production from current levels for the second half of the year," the IEA said in its monthly Oil Market Report.
In another arena generating geopolitical risk for oil markets, Iran and six world powers started three days of talks in Vienna on Wednesday aimed at drafting an agreement for Tehran to curb its nuclear program in exchange for a phased end to sanctions that halved Iran's oil exports over the last two years.
OPEC countries could reduce their own oil output to make room for increased production from Iran, Iran's oil minister said on Wednesday.
(Additional reporting by Christopher Johnson in London and Keith Wallis in Singapore; Editing by Chris Reese)