* Facebook falls on warning of slowing revenue growth
* UK court rules parliament approval must to trigger Brexit
* Crude oil edges up after four-day fall
* Indexes up: Dow 0.24 pct, S&P 0.21 pct, Nasdaq 0.16 pct (Updates to open)
By Tanya Agrawal
Nov 3 (Reuters) - The S&P 500 and the Dow were higher at the open on Thursday, with the benchmark index on track to snap a seven-day losing streak, although a fall in Facebook's shares capped gains on the Nasdaq.
Tension in markets, rattled by U.S. election nerves, eased after a UK court ruling that parliament must approve a government decision to trigger Brexit.
Facebook fell 4 percent to $122.25, a day after the social media giant warned that revenue growth would slow this quarter.
The S&P 500 ended lower on Wednesday for a seventh straight session, its longest such streak in five years, as the Federal Reserve signaled it could hike interest rates in December and the uncertainty surrounding the U.S. election.
The U.S. central bank held interest rates steady, but said the economy had gained steam and job gains remained solid. Policymakers also expressed more optimism that inflation was moving towards their 2 percent target.
Investors have been unnerved by a tightening race between Democrat Hillary Clinton and Republican Donald Trump before next week's presidential election.
While some polls put Trump ahead on Tuesday, an average of polls compiled by the RealClearPolitics website showed Clinton retaining a slight lead. A Reuters/Ipsos daily tracking poll released late on Wednesday showed Clinton ahead by 6 percentage points among likely voters.
"The market is having a bit of a rethink about the slide in the past few days, and the UK court decision this morning is also lifting equities a little bit," said Michael Baughen, global investment specialist at JP Morgan Private Bank in Tampa, Florida.
"However, we remain in a risk-off, low-conviction-trading environment until the election next week."
At 9:41 a.m. ET (1341 GMT) the Dow Jones industrial average was up 43.28 points, or 0.24 percent, at 18,002.92.
The S&P 500 was up 4.37 points, or 0.21 percent, at 2,102.31.
The Nasdaq Composite was up 7.98 points, or 0.16 percent, at 5,113.54.
Seven of the 11 major S&P 500 sectors were higher, with the consumer discretionary index's 0.61 percent rise leading the advancers.
Gold slipped 0.3 percent after touching $1,300 an ounce earlier in the day. The precious metal hovered near its one-month high on Tuesday.
Crude oil futures edged up, supported by news of an attack on a Nigerian oil pipeline and a weaker U.S. dollar, after four days of falls over scepticism that a global glut in crude supplies could be stemmed.
Data on Thursday showed the number of Americans filing for unemployment benefits rose to near three-month high last week, but remained below a level associated with a strong labor market.
A report from the Institute of Supply Management is expected to show that the non-manufacturing activity index dropped to 56.0 in October from 57.1 in September. The data is due at 10 a.m. ET.
Another set of data is likely to show factory orders added 0.2 percent in September.
Fitbit sank 28.6 percent to $9.13 after the wearable fitness device maker's revenue forecast for the key holiday shopping quarter fell well below estimates.
Whole Foods Market rose 4.3 percent to $29.70 after the company said sales declines at established stores are easing.
First Solar fell 11.9 percent to $35.78 after it said a slide in panel price was harming bookings.
Advancing issues outnumbered decliners on the NYSE by 1,647 to 881. On the Nasdaq, 1,390 issues rose and 796 fell.
The S&P 500 index showed no new 52-week highs and six new lows, while the Nasdaq recorded 12 new highs and 45 new lows. (Reporting by Tanya Agrawal; Editing by Anil D'Silva)