* ECB leaves rates unchanged but closes door to further cuts
* Comey testimony expected at 10 a.m. ET
* Alibaba higher after profit forecast
* Futures up: Dow 10 pts, S&P 2.25 pts, Nasdaq 14.25 pts (Adds details, comment, updates prices)
By Tanya Agrawal
June 8 (Reuters) - U.S. stock index futures pared early gains on Thursday after the European Central Bank left rates unchanged but adopted a more hawkish tone, while investors awaited a testimony by former FBI Director James Comey.
The currency bloc's economy has been on its best run since the global financial crisis nearly a decade ago but the ECB was expected to take a more cautious stance as the inflation rebound has yet to show a convincing upward trend.
"The bias is towards higher rates globally over a long-term period and whether the central banks raise rates today or six months from now, I don't think it's going to change things much," said Mike Mattioli, portfolio manager at Manulife Asset Management in Boston.
Comey will be grilled by Washington politicians later over his claims that Trump asked him to drop an investigation of former national security adviser Michael Flynn as part of a probe into Russia's alleged meddling in the 2016 presidential election.
Comey's written testimony on Thursday did not spring a surprise, easing concerns that any new revelation could have dampened already flagging momentum for U.S. President Donald Trump's agenda of lower taxes and lax regulations.
Bets that Trump can implement his agenda are partly behind a rally that has taken stock indexes to record highs.
"Comey might move the markets in the short term but I don't think it's going to affect the intrinsic values of what many large U.S. businesses are worth," said Mattioli.
"While today's events may seem newsworthy in the short-term, I don't think it's going to be needle moving for global economies."
Dow e-minis were up 10 points, or 0.05 percent, with 16,396 contracts changing hands at 8:30 a.m. ET (1230 GMT).
S&P 500 e-minis were up 2.25 points, or 0.09 percent, with 117,032 contracts traded.
Nasdaq 100 e-minis were up 14.25 points, or 0.24 percent, on volume of 23,494 contracts.
Investors are also keeping an eye on the outcome of the UK general election, with opinion polls showing Theresa May's Conservative Party leading between 5 and 12 percentage points over the main opposition Labour Party, suggesting she would increase her majority.
Oil fell for a second day to hit one-month lows after an unexpected surge in U.S. inventories and the return of more Nigerian crude aggravated investor concerns about an already oversupplied market.
Shares of Alibaba Group Holding were up 14.1 percent at $143.50 in premarket trading after the company said it expects revenue growth of 45-49 percent in the 2018 fiscal year.
Yahoo, which owns a 15.5 percent stake in Alibaba also rose 10.4 percent to $55.80.
Greif fell 8.8 percent to $54.5 after the industrial packaging products company's quarterly profit missed estimates. (Reporting by Tanya Agrawal in Bengaluru; Editing by Anil D'Silva)