* Retailers post mixed monthly sales in January
* Greenlight Capital sues Apple
* Futures up: Dow 3 pts, S&P 1.3 pts, Nasdaq 9.25 pts
NEW YORK, Feb 7 (Reuters) - U.S. stocks were poised for a flat open on Thursday after data showed modest improvement in the labor market and retailers posted mixed monthly sales.
Weekly initial jobless claims dipped by 5,000 to 366,000, with the four-week moving average falling to its lowest level since March 2008, signaling the economy continues to recover slowly.
A separate report said fourth-quarter, productivity registered its biggest drop in nearly two years, while unit labor costs jumped 4.5 percent, more than economists expected.
"Claims didn't look too exciting. They are pretty much in line. The bigger surprise was the jump in unit labor costs that was pretty substantial," said Peter Jankovskis, co-chief investment officer at OakBrook Investments LLC in Lisle, Illinois.
"Overall the market took the whole thing in stride."
Recent data has pointed to a slow improvement in the economy, but one without enough strength to cause the Federal Reserve to abandon its easy monetary policy, which has helped the benchmark S&P index to climb 6 percent this year.
"We are probably in a pretty stable policy regime from the Fed standpoint, certainly until midyear, then as we get later in the year if we are seeing the economy picking up, then maybe they start taking their foot off the accelerator a little bit," said Jankovskis.
Several U.S. retailers reported mixed January sales results, as consumers faced a hit to their take-home pay from higher payroll taxes.
Macy's Inc rose 3.8 percent to $40.98 before the opening bell after reporting January same store sales rose 11.7 percent.
Ann Inc dropped 9.3 percent to $29.75 in premarket trading after forecasting fourth-quarter sales below analysts' expectations.
S&P 500 futures rose 1.3 points and were roughly even with 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 gained 3 points, and Nasdaq 100 futures added 9.25 points.
Fund manager David Einhorn's Greenlight Capital on Thursday said it has sued Apple Inc and said the company needs to do more to unlock value for shareholders. Apple shares gained 1.6 percent to $464.87 in premarket trading.
Sprint Nextel edged down 0.5 percent to $5.74 as the No. 3 U.S. mobile service provider posted higher fourth-quarter revenue, but its subscriber numbers disappointed Wall Street.
According to Thomson Reuters data through Wednesday morning, of 301 companies in the S&P 500 that have reported earnings, 68.1 percent have exceeded analysts' expectations, above a 62 percent average since 1994 and 65 percent over the past four quarters. In terms of revenue, 65.8 percent of companies have topped forecasts.
Fourth-quarter earnings for S&P 500 companies rose 4.7 percent, according to the data, above a 1.9 percent forecast at the start of the earnings season.
The European Central Bank held its main interest rate unchanged at 0.75 percent, as expected.