* Futures up: Dow 38 pts, S&P 4 pts, Nasdaq 13 pts
By Tanya Agrawal
June 8 (Reuters) - U.S. stock index futures were slightly higher on Thursday, a day after written testimony from former FBI director James Comey did not spring a surprise, while investors remained focused on an ECB meeting and the UK election outcome.
* Investors were concerned that any new revelation by Comey, who was fired by President Donald Trump last month, could dampen already flagging momentum for Trump's agenda of lower taxes and lax regulations.
* 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.
* Bets that Trump can implement his agenda are partly behind a rally that has taken stock indexes to record highs.
* 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.
* Meanwhile, the ECB is likely to keep its easy monetary policy during its meeting as inflation remains below its target, despite stronger economic growth in the euro zone.
* Oil edged up, having hit one-month lows the previous day after an unexpected surge in U.S. inventories and the return of more Nigerian crude to an already oversupplied market.
* Shares of Alibaba Group Holding were up 11.5 percent at $140.08 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 8.8 percent to $55.
* Pandora Media was up 2.6 percent at $8.70 after sources told Reuters that Sirius XM Holdings is seeking to invest in the internet music provider. Sirius edged up 0.6 percent.
Futures snapshot at 7:04 a.m. ET:
* Dow e-minis were up 38 points, or 0.18 percent, with 12,149 contracts changing hands.
* S&P 500 e-minis were up 4 points, or 0.16 percent, with 90,286 contracts traded.
* Nasdaq 100 e-minis were up 13 points, or 0.22 percent, on volume of 16,168 contracts. (Reporting by Tanya Agrawal in Bengaluru; Editing by Anil D'Silva)