The Dow Jones Industrial Average slipped 24.75 points, or 0.20 percent, to close at 12,602.26. The Dow was down as many as 176 points at its lowest.
The S&P 500 erased 2.81 points, or 0.21 percent, to end at 1,329.04. The Nasdaq declined 25.83 points, or 0.90 percent, to finish at 2,849.49. The Nasdaq earlier briefly turned negative for the month of June. The CBOE Volatility Index, widely considered the best gauge of fear in the market, closed above 19.
In the last week, Merkel had refused to discuss the issue of debt burden sharing unless national budget controls across the euro zone are introduced first. (Read More: From Nazi to Terminator, Europe's Media Target Merkel) Meanwhile, a spokesman for German Finance Minister Wolfgang Schaeuble said that a report that Germany could be willing to move sooner than expected to accept shared liability of euro zone debt was not true.
Italian bond yields spiked to their highest level since December 2011 following 5- and 10-year bond auctions ahead of the summit.
The Supreme Court upheld the individual health insurance requirementin President Obama's health-care law, a victory for Democrats and Obama. (Read More: What Is the Health Insurance Mandate?)
Obama called the Supreme Court's decision "a victory for people across the country," while Mitt Romney said he will work "on my first day as president" to repeal the law if he's elected in November.
Medicaid-related stocks such as Amerigroup and Molina jumped following the announcement. And hospital stocks including Universal Health, Community Health and Tenet Healthcare rallied.
But most managed care companies such as Cigna , Wellpoint and Aetna dragged.
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Experts were mixed on the announcement.