* Crude futures fail to recover Thursday's losses
* Asia stocks slip despite Wall Street scaling new highs
* Sterling tumbles on PM May's shrinking election lead, UK GDP
* Dollar little changed as economic data show mixed performance
SINGAPORE, May 26 (Reuters) - Crude prices were on the defensive on Friday after an agreement by OPEC to extend existing supply curbs disappointed investors wagering on larger cuts, prompting a move away from riskier assets and depressing Asian stocks.
Sterling continued its decline after a poll showing British Prime Minister Theresa May's lead narrowing less than two weeks before the election came on the heels of disappointing economic data on Thursday.
The Organization of Petroleum Exporting Countries and some non-OPEC producers agreed at a meeting in Vienna on Thursday to extend supply cuts of 1.8 million barrels per day until the end of the first quarter of 2018.
While OPEC's move had been expected, some oil market investors had hoped producers would agree to longer or deeper cuts to drain a global glut of oil.
Talk around extending the cuts had driven crude futures higher in recent days, with the confirmation prompting profit-taking.
"This seems like a clear case of buy the rumor, sell the fact, which was touted to be the reaction," James Woods, global investment analyst at Rivkin Securities in Sydney, wrote in a note.
U.S. crude prices were flat at $48.88 on Friday, after losing 4.8 percent overnight, set to end the week 2.8 percent lower.
Global benchmark Brent inched about 0.1 percent higher to $51.50, after slumping 4.6 percent overnight. It is on track for a 3.9 percent weekly loss. MSCI's broadest index of Asia-Pacific shares outside Japan , which closed at a two-year high on Thursday, fell 0.2 percent, shrinking its weekly gain to 1.4 percent.
Japan's Nikkei also slipped 0.2 percent, on track for a 0.9 percent increase for the week.
Australia's benchmark lost 0.75 percent, poised for a 0.3 percent weekly rise.
China's CSI 300 was flat, heading for a 2.4 percent increase for the week. Hong Kong's Hang Seng advanced about 0.1 percent, extending its weekly gain to 1.85 percent.
Overnight on Wall Street, the S&P 500 and the Nasdaq closed at record highs after strong earnings reports from retailers.
The strong performance helped lift MSCI's global stocks index to a record close overnight.
Sterling fell 0.4 percent on Friday to $1.2906, its biggest one-day slide in over three weeks, after a YouGov poll showed Britain's opposition Labour Party had cut the lead of Prime Minister May's Conservatives to five points, less than a fortnight before a national election.
That came after the currency lost 0.3 percent on Thursday following data that showed Britain's economy slowed more than previously thought in the first quarter of this year.
"The UK is now beginning to look like the sick man of Europe," said Kathleen Brooks, research director with City Index in London.
The dollar pulled back 0.2 percent to 111.57 yen on Friday, but was set to end the week up 0.3 percent.
The dollar index, which tracks the greenback against a basket of six major peers, added 0.1 percent, poised for a 0.2 percent gain for the week.
U.S. unemployment data that showed a tightening labor market was offset by a widening goods trade deficit in April and news of declining inventories, prompting analysts to pare their second-quarter economic growth estimates.
The euro retreated 0.1 percent to $1.1198.
Gold rose 0.2 percent to $1,257.71 an ounce, poised for a 0.2 percent gain for the week. (Reporting by Nichola Saminather; Additional reporting by Patrick Graham; Editing by Eric Meijer & Shri Navaratnam)