U.S. stocks weakened on Tuesday as disappointing sales from Johnson & Johnson stirred jitters about the strength of earnings, snapping the S&P 500's six-day winning streak.

With the last two earnings periods characterized by cost cutting, investors have been hopeful that companies may start to show revenue growth in third-quarter results or improved outlooks.

Though investors remain optimistic about the earnings season, the hope for strong revenue could be premature. Indeed, Johnson & Johnson beat Wall Street's earnings expectations, but reported revenue that was below forecasts, sending its shares down 2.4 percent to $61.01.

People are on the edge of their seats, said Ronald Knipping, managing principal at the wealth management division of Rehmann, a Michigan-based financial advisory firm.

The leading indicator is going to be revenue growth, and right now there's none.

Financial shares were pressured, with several major banks reporting results this week. Goldman Sachs Group Inc fell 1.5 percent to $187.23 after influential banking analyst Meredith Whitney downgraded the stock, saying the upside could be limited for the company in the medium term.

The Dow Jones industrial average <.DJI> declined 14.74 points, or 0.15 percent, to end at 9,871.06. The Standard & Poor's 500 Index <.SPX> slipped 3.00 points, or 0.28 percent, to 1,073.19. But the Nasdaq Composite Index <.IXIC> inched up just 0.75 of a point, or 0.04 percent, to 2,139.89.

The Nasdaq stayed above water after Cisco Systems Inc agreed to buy Starent Networks Corp for $2.9 billion, or $35 per share. Cisco's stock added 0.5 percent to $23.89, while Starent, which makes telecommunications equipment, surged 16.8 percent to $33.91.

Healthcare stocks slid after a key Senate committee endorsed a sweeping healthcare overhaul as it gained the support of an influential Republican. The proposal will be merged with the Senate health panel's version and moved to the full Senate for debate in the next few weeks.

The Morgan Stanley Healthcare Payor index <.HMO> fell 2.3 percent on concerns about what a potential healthcare overhaul would mean for health insurers' profits.

The S&P financial index <.GSPF> lost 1.1 percent, with JPMorgan Chase & Co , Citigroup Inc , Goldman Sachs and Bank of America all reporting throughout the week.

(Additional reporting by Ellis Mnyandu; Editing by Jan Paschal)

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