* Nike up in premarket after results; DuPont cuts outlook
* Russell reconstitution may drive up volume at close
* Final June consumer sentiment data due after market open
* Futures down: Dow 26 pts, S&P 500 4.25 pts, Nasdaq 5.5 pts
By Ryan Vlastelica
NEW YORK, June 27 (Reuters) - U.S. stock index futures fell on Friday, with major indexes largely on track to close out a week of modest losses as investors grew cautious over the state of economic growth.
* While the S&P 500 remains 0.3 percent away from a record closing high, further gains may be difficult to come by following some negative data and comments from St. Louis Fed President James Bullard, who said interest-rate increases should come sooner rather than later.
* Ongoing violence in Iraq continues to be a concern for investors, as prolonged tension in the region could cause a prolonged spike in crude oil prices and weigh on consumer spending.
* Nike Inc reported fourth-quarter earnings that beat expectations on strong sales in North America and Europe, while DuPont cut its full-year operating profit outlook, citing weakness in its agriculture and performance chemicals divisions.
* News on both companies, which are Dow components, came after the market closed on Thursday. Nike rose 3.2 percent to $79.35 in premarket trading.
* S&P 500 e-mini futures fell 4.25 points and were below fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average e-mini futures fell 26 points and Nasdaq 100 e-mini futures lost 5.5 points.
* For the week, the Dow is down 0.6 percent and the S&P is down 0.3 percent. The Nasdaq, which is up 0.3 percent, is on track for its sixth weekly rise out of the past seven. The CBOE Volatility index is up 7.2 percent this week.
* Volume may be heavy going into the close on Friday, when Russell Investments announces the final reconstitution of its indexes, which will affect more than $5 trillion in assets.
* Market participants are looking ahead to the final read on June consumer sentiment from the Thomson Reuters/University of Michigan Surveys of Consumers at 9:55 a.m. EDT (1355 GMT), which is seen rising slightly to 82 from 81.2. The report follows a weaker-than-expected report on consumer spending earlier this week, as well as an unexpectedly wide contraction in first-quarter economic activity.
* In company news, Relational Investors LLC late Thursday disclosed an 8.52 percent stake in Manitowoc Co Inc and said it was embarking on a plan to separate it into two companies. (Editing by Bernadette Baum)