* Asia ex-Japan, Nikkei both poised for weekly losses
* EM index slumps on Brazil fears; real maintains losses
* Wall Street recovers overnight from worst sell-off in 8 months
* Dollar surrenders some gains as U.S. political concerns linger
* U.S. crude set for best week since March on supply cut optimism
SINGAPORE, May 19 (Reuters) - Asian stocks were mixed on Friday, while the dollar surrendered some of the overnight gains it made on strong economic data amid ongoing political turbulence around U.S. President Donald Trump.
MSCI's broadest index of Asia-Pacific shares outside Japan slipped 0.1 percent, on track for a weekly loss of 0.5 percent.
Japan's Nikkei reversed early gains to trade 0.15 percent lower, extending declines for the week to 1.8 percent for the week.
Chinese shares added 0.1 percent, up 0.4 percent for the week. Hong Kong's Hang Seng advanced 0.2 percent, set for a weekly rise of 0.1 percent.
"The trend we have seen with Asian markets this morning has been one of mixed performances," said Jingyi Pan, market strategist at IG in Singapore.
"While U.S. markets managed to stage a moderate recovery with investors finding good entry points after the heavy sell-off, Asian investors are likely choosing to err on the cautious side, especially with multiple event risks in the week ahead."
These events included testimony by former FBI director James Comey at a Senate hearing and an OPEC meeting in Vienna, she added.
Trump's dismissal of Comey last week set off a political firestorm that culminated on Wednesday in Wall Street's biggest sell-off in over eight months.
The Justice Department's appointment of former FBI chief Robert Mueller as special counsel to probe possible ties between Russia and Trump's 2016 presidential campaign helped calm markets and lifted Wall Street on Thursday.
The Dow gained 0.3 percent, the S&P was up 0.4 percent and the Nasdaq jumped 0.7 percent.
"We could be just shaking off the jitters here. Yesterday, investors were really worried," said Janna Sampson, co-chief investment officer at OakBrook Investments LLC in Lisle, Illinois.
"Whatever the (investigation) result, people feel they might have confidence it's an accurate, unbiased result," she said.
MSCI's emerging markets index extended losses by 0.15 percent on Friday.
It posted its lowest close in almost two weeks on Thursday, dragged down by an 8.8 percent slump in Brazilian stocks , on a report that President Michel Temer supported an attempt to bribe a potential witness to remain silent in the country's biggest-ever graft probe.
The Brazilian real was fractionally weaker at 3.3685 per dollar early on Friday, after plunging as much as 8.5 percent to its lowest level since December on Thursday.
Strong economic indicators from the U.S. helped lift the dollar overnight, but it slipped back on Friday.
It weakened 0.25 percent to 111.225 yen, erasing some of Thursday's 0.6 percent gain, and was set for a 1.8 percent fall over the week.
Data showed a sharp acceleration in factory activity in the mid-Atlantic region in May, and an unexpected drop in new applications for unemployment benefits.
The dollar index, which tracks the greenback against a basket of six major peers, was slightly lower at 97.824, after gaining 0.3 percent on Thursday. It's set to end the week 1.4 percent lower.
Sterling was little changed at $1.2945.
On Thursday, it broke through $1.30 for the first time in almost eight months after news of better-than-expected British retail sales growth helped ease concerns about the broader economy. But it fell back on technical selling to close 0.2 percent lower.
The euro was little changed at $1.11 on Friday. It touched a six-month high on Thursday but surrendered the gains as the dollar advanced to close 0.5 percent lower.
In commodities, oil prices continued their gains for the third straight session, set to post a 4 percent rise, on optimism that producers will agree to rein in output for longer.
U.S. crude futures hit a three-week high, and were last trading up 0.8 percent to $49.75 a barrel.
Global benchmark Brent was up 0.7 percent at $52.88, after touching a four-week high earlier in the session.
Gold inched higher, clawing back some of Thursday's losses. Spot gold added 0.25 percent to $1,249.84 an ounce, set to post a weekly gain of 1.7 percent. (Additional reporting by Sinead Carew; Editing by Simon Cameron-Moore and Eric Meijer)