The S&P 500 and Dow were slightly lower on Friday amid renewed concerns over euro zone debt, but strong results in the tech sector helped keep the Nasdaq in positive territory.

Moody's downgraded Ireland's ratings by five notches, hitting European bank shares hard. Euro zone leaders have agreed on how to resolve debt crises from 2013, but failed to reassure markets about what they will do in the short term.

U.S.-listed shares of Allied Irish Bank fell 3.9 percent to $1.24 while Barclays dropped 2.7 percent to $16.15. However, the impact on U.S. shares not directly linked to the Irish situation were limited.

There are more shoes to drop in Europe, but precedent has been set to help these countries. That's why equity markets aren't reacting significantly negatively to the news, said Michael Gault, a senior portfolio strategist at the New York-based Weiser Capital Management, which has about $150 million in assets under management.

Unless that support won't be there, I think investors will in general be able to shake off the news and find positives, like the tech results, he added.

Shares of both Oracle Corp and Research in Motion rallied a day after they posted strong quarterly results. Oracle also issued an upbeat forecast.

Oracle gained 5.5 percent to $31.94 while U.S.-listed shares of RIM were up 3.4 percent to $61.23.

The Dow Jones industrial average <.DJI> was down 20.59 points, or 0.18 percent, at 11,478.66. The Standard & Poor's 500 Index <.SPX> was up 0.25 points, or 0.02 percent, at 1,243.12. The Nasdaq Composite Index <.IXIC> was up 8.21 points, or 0.31 percent, at 2,645.52.

Regional banks traded higher after Canada's Bank of Montreal agreed to buy Marshall & Ilsley Corp for $4.1 billion, sending the stock up 18 percent to $6.84.

Peer regional bank KeyCorp climbed 3.2 percent to $8.35 while Regions Financial added 3.4 percent to $6.34.

The KBW Regional Banks index <.KRX> rose 0.7 percent and has risen more than 13 percent this year, including a gain of more than 12 percent in December alone despite continued debt woes from European banks.

Mergers and acquisitions are up for the first full year since 2007 and may mark the start of a new, multiyear M&A cycle, with emerging economies accounting for a bigger share of global dealmaking, according to Thomson Reuters data.

With the S&P 500 up 5 percent in December, some technical analysts say the market is due for a pullback before the year's end.

We've had an unanswered rally in the market for months now, and our great fundamental news is being offset by technical conditions, said Wayne Wilbanks, chief investment officer of Wilbanks, Smith & Thomas in Norfolk, Virginia, which has $1.7 billion assets under management.

We're above both the 50-day and 200-day moving averages, and that's offsetting and nullifying the good news that's coming out on earnings.

Market volume and volatility could increase later in the day as traders adjust or exercise derivative positions on four different types of expiring equity futures and options contracts, also know as quadruple witching.