U.S. stocks swung between gains and losses, with the Standard & Poor’s 500 Index at a one-month low, as a drop in technology and energy shares overshadowed optimism the world’s largest economy will weather Europe’s debt crisis.

Chancellor Angela Merkel and U.K. Prime Minister David Cameron failed to reconcile their differences on German plans for European Union treaty change and a financial transaction tax, as Cameron called for “decisive action” to stem the euro-area debt crisis. Merkel said changes to EU treaties to allow for greater fiscal integration should be approved only by the 17 nations that share the euro, while Cameron wants changes to be approved more widely to allow him to take back powers from Brussels. Cameron also suggested Germany support calls to allow the European Central Bank to fund purchases of troubled sovereign debt.

Stocks erased gains earlier today after Deutsche Presse- Agentur reported that Germany’s Foreign Ministry said the nation was considering the possibility of “orderly defaults” beyond Greece.

Dow 11,788.44 +17.71 +0.15%, Nasdaq 2,576.12 -11.87 -0.46%, S&P 500 1,215.24 -0.89 -0.07%

Halliburton Co. and Schlumberger Ltd. dropped at least 1.6 percent as oil sank 2 percent.

Salesforce.com Inc. (CRM), the largest maker of online customer-management software, lost 9.6 percent after billings missed some estimates.

Boeing Co. (BA) rose 1.7 percent after winning a provisional order for 230 planes from Lion Air.

H.J. Heinz Co. fell 3.3 percent as the world’s biggest ketchup maker affirmed its forecast current fiscal year earnings of no more than $3.32 a share. Analysts are on average estimating $3.34 a share, according to a Bloomberg survey.

Hewlett-Packard Co. (HPQ) rose the most in the Dow Jones Industrial Average, gaining 2.5 percent. The largest computer maker appointed activist shareholder Ralph Whitworth of Relational Investors LLC to its board after he accumulated an almost 1 percent stake.