* Futures down: Dow 61 pts, S&P 6 pts, Nasdaq 13 pts
By Tanya Agrawal
May 13 (Reuters) - U.S. stock index futures were lower on Friday as oil prices fell and investors awaited April retail sales data for clues on the strength of the economy.
* U.S. retail sales likely surged in April as households stepped up purchases of cars and light trucks. According to a Reuters survey of economists, retail sales probably rose 0.8 percent last month after falling 0.4 percent in March. The data is expected at 8:30 a.m. ET (1230 GMT).
* However, weak earnings from department stores including Macy's this week has spooked investors. Consumer spending accounts for more than two-thirds of U.S. economic activity.
* Oil ended a three-day bull run on Friday, falling as a strong dollar made it more expensive to hold positions.
* U.S. stocks ended mixed on Thursday, with gains in telecommunications and consumer staples helping make up for Apple's tumble to a two-year low. Apple was down 0.4 percent at $90.01 in premarket trading.
* A rally in the S&P 500 index from its February lows has petered out over the last two weeks amid underwhelming earnings reports from companies and economic data that clouded the outlook for interest rate increases this year.
* Two U.S. Federal Reserve officials said on Thursday that the central bank should raise rates if data points to an improving economy. However, traders are pricing in only rate hike, at the end of the year.
* Department store operator Nordstrom's shares were down nearly 18 percent at $37.11 after weak results.
* Nvidia was up 7.2 percent at $38.15 after the company forecast better-than-expected revenue for the current quarter.
* UnitedHealth was down 2.8 percent at $126 after a judge ruled in favor of Republicans who challenged President Barack Obama's healthcare law, ruling that his administration had overstepped its constitutional powers on government spending.
Futures snapshot at 6:59 a.m. ET:
* S&P 500 e-minis were down 6 points, or 0.29 percent, with 188,688 contracts traded.
* Nasdaq 100 e-minis were down 13 points, or 0.3 percent, on volume of 25,238 contracts.
* Dow e-minis were down 61 points, or 0.35 percent, with 28,674 contracts changing hands. (Reporting by Tanya Agrawal; Additional reporting by Yashaswini Swamynathan; Editing by Ted Kerr)