* S&P 500 has gained 1.9 percent over past two sessions
* Fourth-quarter GDP may be revised to show growth
* J.C. Penney, Groupon both sink on weak revenue
* Futures up: Dow 16 pts, S&P 2.7 pts, Nasdaq 4.5 pts
By Ryan Vlastelica
NEW YORK, Feb 28 (Reuters) - U.S. stock index futures edged modestly higher on Thursday as investors were reluctant to make big bets following a sharp two-day rally and ahead of a rash of data.
* Investors will also be keeping an eye on the debate in Washington over sequestration - U.S. government budget cuts that will take effect starting on Friday if lawmakers fail to reach an agreement on spending and taxes. President Barack Obama and Republican congressional leaders arranged to hold last-ditch talks to prevent the cuts, but expectations were low that any deal would be produced.
* Major indexes posted their biggest daily gains since early January on Wednesday, putting the S&P 500 back above the closely watched level of 1,500. Over the past two sessions, the index has gained 1.9 percent, lifted by strong data and comments from Federal Reserve Chairman Ben Bernanke that showed continued support for the Fed's stimulus policy.
* Wall Street has largely resisted predictions it would undergo a correction, with the S&P up 6.3 percent so far this year and the Dow Jones industrial average within striking distance of an all-time high. While markets suffered steep losses earlier this week on concerns over European debt, they have since recovered and are flat on the week.
* Revised gross domestic product data is expected to show that the U.S. economy grew 0.5 percent in the fourth quarter, rather than contracted 0.1 percent as initially estimated. The data is due at 8:30 a.m. (1330 GMT)
* Weekly jobless claims, also on tap for 8:30 a.m., are seen dipping by 2,000 to 360,000 in the latest week, while the February Chicago PMI is seen dipping to 54.3 from 55.6 last month.
* Those reports come in the wake of strong pending home sales data Wednesday and a proxy for business spending plans that was more robust than expected, which added to the positive tone in markets.
* S&P 500 futures rose 2.7 points and were above 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 futures added 16 points and Nasdaq 100 futures rose 4.5 points.
* J.C. Penney Co Inc shares slumped 15 percent to $18.01 in premarket trading a day after it reported a steep drop in sales, prompting the department store to overhaul its pricing strategy.
* Groupon Inc also reported revenue that missed expectations, sending shares down 26 percent to $4.41 before the bell.
* Salesforce.com Inc and Gap Inc are on tap to report results later Thursday.
* With 93 percent of the S&P 500 companies having reported results so far, 69.5 percent have beaten profit expectations, compared with a 62 percent average since 1994 and 65 percent over the past four quarters, according to Thomson Reuters data.
* Fourth-quarter earnings for S&P 500 companies are estimated to have risen 6.2 percent, according to the data, above a 1.9 percent forecast at the start of the earnings season.
* Tim Cook, chief executive of Apple Inc, acknowledged widespread disappointment Wednesday in the performance of the tech titan's stock, which is down 16.5 percent so far this year, but urged investors to take a long-term view on the company.