(For a Reuters live blog on U.S., UK and European stock markets, click LIVE/ or type LIVE/ in a news window.) * Futures: Dow off 0.1%, S&P flat, Nasdaq up 0.5% March 31 (Reuters) - S&P 500 futures were flat on Wednesday, as investors awaited details of how President Joe Biden would fund a massive infrastructure plan, while Wall Street headed for its fourth straight quarterly gain on signs of a strong economic rebound. The $3 trillion-$4 trillion package will target traditional projects like roads and bridges alongside investments in the electric vehicle market. The size and scale of the proposal as well as the question of how it would be paid for is likely to set the stage for the next partisan clash in Congress. Unprecedented stimulus and a swift vaccine rollout in the United States have helped the S&P 500 and the Dow hit record closing highs last week. The U.S. 10-year bond yield rising to 14-month highs hurt high-flying tech names, keeping the Nasdaq 7.5% from its all-time peak. At 06:29 a.m. ET, Dow E-minis were down 43 points, or 0.13%, and S&P 500 E-minis were up 1.25 points, or 0.03%. Nasdaq 100 E-minis were up 68.5 points, or 0.53%, as Apple Inc rose 1.6% after brokerage UBS upgraded the stock to “buy” on stable long-term demand for iPhones with better authorized service providers. After leading Wall Street’s rally from the coronavirus-lows of last year, the Nasdaq’s 1.2% gain has lagged the S&P 500 and the Dow this quarter as investors swapped growth-oriented stocks with underpriced shares deemed to benefit most from an economic rebound. Later in the day, private payrolls data for March, a precursor to the more comprehensive monthly jobs report on Friday, will give investors a reading on the state of the labor market. (Reporting by Medha Singh in Bengaluru; Editing by Arun Koyyur)