By Leah Schnurr

NEW YORK (Reuters) - Wall Street may have momentum on its side next week as the S&P 500 tries to puncture the 1,000 level, but the rally's staying power will depend on whether U.S. data and corporate earnings provide more signs of economic stabilization.

In a busy week of data, the most crucial report will be a look at the number of jobs lost in July as measured by the Labor Department's non-farm payrolls report.

While unemployment is expected to remain high even as the economy begins to recover, analysts are anticipating the data will show the economy shed fewer jobs than the month before.

Among companies expected to release results are Dow components Procter & Gamble (PG.N), Kraft (KFT.N) and Cisco

(CSCO.O).

The broad Standard & Poor's 500 index .SPX recorded its best five-month streak since 1938 on Friday with July's gains as more corporate earnings beat expectations and data suggested the worst of the economic slump was over.

More companies will release their quarterly scorecards, though the bulk of the earnings season is out of the way with 67 percent of S&P companies having reported. The better-than-expected results have driven the most recent leg of the rally.

But with a 46 percent gain from March's 12-year low, the S&P 500 could be ripe for a pullback, especially if the week's data is less encouraging.

"I still sense from the portfolio managers and traders we deal with that even though we have nice upside momentum, they have their fingers on the trigger and aren't going to stick around if some bad data comes out," said Brian Daley, sales trader at Conifer Securities in New York.

BUY SIGNAL

Investors will be watching the S&P to see if it can breach 1,000, a key technical and psychological mark. The market will face resistance getting to that point, but piercing 1,000 could also be perceived as a buy signal, causing the market to rally even higher.

The market tested the level earlier in the week, coming within about 4 points but was unable to get any further.

"The price movements have been dramatic and impressive," said Keith Springer, president of Capital Financial Advisory Services in Sacramento, California.

"The volume has not been as impressive. I think that we're going to have to see better data in the weeks ahead to actually support it."

So far, 74 percent of S&P companies that have reported have beaten Wall Street's expectations, according to data from Thomson Reuters. Analysts point out that the expectations were a low hurdle to jump, questioning the strength of results that have come on the back of cost cutting and layoffs.