Wall Street ended flat as the latest deal news offset losses following soft data on the housing market and services sector. The market may also be hitting resistance with the Dow Jones industrial average sitting just below 17,000 and the S&P 500 near 2,000.

"Technically, we are battling round numbers that I think give investors reason to pause," said Todd Salamone, senior vice president of Research, Schaeffer's Investment Research in Cincinnati.

The U.S. dollar traded mostly flat against a basket of major currencies, halting last week's advance but still hovering near six-month highs.

Investors and traders were hesitant to make bold moves on concerns over new European sanctions against Moscow and ahead of Wednesday's release of U.S. second-quarter gross domestic product. The calendar also includes a Federal Reserve policy announcement on Wednesday and U.S. nonfarm payrolls data Friday.

Economists forecast U.S. GDP grew 3 percent in the second quarter after a sharp contraction of 2.9 percent in the first quarter, and expect U.S. employers to have added 233,000 jobs in July, according to Reuters polls.

The Dow Jones industrial average rose 22.02 points or 0.13 percent, to 16,982.59, the S&P 500 gained 0.57 points or 0.03 percent, to 1,978.91 and the Nasdaq Composite dropped 4.66 points or 0.1 percent, to 4,444.91.

MSCI's All-World Index was up 0.01 percent.

Among deal news on Wall Street, Dollar Tree Inc offered to buy rival discount chain Family Dollar Stores Inc for about $8.5 billion (£5 billion) while Zillow Inc agreed to buy Trulia Inc for $3.5 billion in stock.

Russian markets tumbled for a third straight session after the European Union reached an outline agreement on its first economic sanctions on Russia since the downing of a Malaysian airliner in rebel-held eastern Ukraine.

Moscow's dollar-denominated RTS index slumped 3 percent, the rouble-traded MICEX fell 1.9 percent and the rouble dropped half a percent against both the dollar and the euro.

"We have seen Germany stepping up rhetoric on tougher sanctions on Russia," said Vasileios Gkionakis, Global Head of FX Strategy for UniCredit in London. "Saying stability and peace is the top priority rather than economic interests are strong words."

An index of European shares lost 0.2 percent.

The U.S. dollar index, which measures the dollar against a basket of six major currencies, was last flat at 81.030. U.S. government bond yields edged higher after dropping on Friday, with the benchmark 10-year U.S. Treasury note down 6/32 in price to yield 2.49 percent.

Oil prices dipped as signs of excess supplies of North Sea and West African crude and weak demand in Europe and Asia offset fears of escalating tensions in Ukraine and the Middle East.

September Brent lost 82 cents to settle at $107.57 a barrel, after reaching a low of $107.01 earlier in the session while U.S. crude futures for September delivery lost 42 cents to settle at $101.67, up from an intraday low of $100.90.

(Reporting by Angela Moon; Editing by Nick Zieminski and James Dalgleish)

By Angela Moon