* Staples, Office Depot in advanced merger talks - WSJ
* Aetna posts Q4 results, raises 2015 outlook
* Futures up: Dow 46 pts, S&P 6.25 pts, Nasdaq 9.5 pts
By Chuck Mikolajczak
NEW YORK, Feb 3 (Reuters) - U.S. stock index futures climbed on Tuesday, with the benchmark S&P 500 index set to continue a rally fueled by hopes of a deal on Greek debt.
* Stocks rallied late in the prior session on signs Greece was softening its approach to debt negotiations. A source told Reuters that Greek Finance Minister Yanis Varoufakis, in London to reassure private investors he was not seeking a showdown with Brussels over a new debt agreement, said the new left-wing government would spare privately held bonds from losses.
* The S&P 500 is still down more than 3 percent from its Dec. 29 record high amid lackluster corporate earnings and data showing the U.S. economy growing at a slower pace than investors anticipated. January's 3.1 percent decline was the worst monthly performance for the index in a year.
* According to Thomson Reuters data through Monday morning, of 226 companies in the S&P 500 that have posted earnings, 73 percent have topped expectations. The expected growth rate for the quarter sits at 5.4 percent, down from 11.2 percent expected on Oct. 1.
* Aetna, the third-largest U.S. health insurer, reported fourth-quarter earnings that matched Wall Street expectations and raised its 2015 forecast for operating earnings.
* Office Depot shares surged 17.8 percent to $8.99 before the opening bell after the Wall Street Journal reported the company is in advanced talks to merge with Staples Inc . Staples shares jumped 10.8 percent to $18.99.
* Economic data expected Tuesday includes December factory orders at 10:00 a.m. (1500 GMT) and U.S. vehicle sales throughout the day.
* European stocks rose, with the pan-European FTSEurofirst 300 index just below a seven-year high on hopes for an agreement on the Greek debt standoff. Athens' benchmark index ATG climbed more than 9 percent.
Futures snapshot at 7:32 a.m. ET (1232 GMT):
* S&P 500 e-minis were up 6.25 points, or 0.31 percent, with 143,949 contracts changing hands.
* Nasdaq 100 e-minis were up 9.5 points, or 0.23 percent, in volume of 25,460 contracts.
* Dow e-minis were up 46 points, or 0.27 percent, with 23,031 contracts changing hands.
Editing by Bernadette Baum