* NATO says Russian troops massing on Ukraine border
* Euro stocks tumble, Wall Street shakes off early weakness
* German industrial orders slide, sanctions bite
* Investors seek refuge in German bonds, yields hit new lows (Adds U.S. market open, quote; changes dateline; previous LONDON)
NEW YORK, Aug 6 (Reuters) - European stocks fell on Wednesday as concerns over a Russian troop build-up on the border with Ukraine sent nervous investors into high-rated bonds, while U.S. stocks shrugged off early weakness and traded higher.
U.S. stocks were pressured, however, by the collapse of several high-profile takeovers. Time Warner Inc, fell 12 percent to $75 after Twenty-First Century Fox pulled its $80 billion bid. Fox was up 6 percent to $33.19.
The S&P 500 was trading just above 1,920, a key technical support level for the index, and is down 3.4 percent since its most recent record high on July 24.
"It's actually similar to the five mini-corrections of 5 percent or so the S&P has experienced since the summer of 2012," said Darrell Cronk, deputy chief investment officer of Wells Fargo Private Bank in New York.
"We continue to have these kinds of mini 3-to-6 percent pullbacks and the market finds a base and moves higher."
The Dow Jones industrial average was up 47.46 points, or 0.29 percent, at 16,476.93. The Standard & Poor's 500 Index was up 5.95 points, or 0.31 percent, at 1,926.16. The Nasdaq Composite Index was up 14.62 points, or 0.34 percent, at 4,367.45.
NATO said Wednesday Russia has amassed around 20,000 combat-ready troops on Ukraine's eastern border and could use the pretext of a humanitarian or peace-keeping mission to invade.
The euro came under pressure, hitting a nine-month low of $1.331 against the dollar amid threats of retaliatory Russian sanctions against the European Union, and signs the crisis in Ukraine was affecting Germany, Europe's biggest economy.
German industrial orders slid in June at the steepest rate since September 2011, and the economy ministry said political tensions had probably led to more consumer caution.
The FTSEurofirst 300 fell 1.2 percent while MSCI's world equity index was down 0.6 percent. Dollar-traded Russian stocks fell more than 2 percent to their lowest level since May 6.
German 10-year bond yields fell 7 basis points to a record low of 1.10 percent, on track for their biggest daily drop in nearly a year.
Yields on lower-rated peripheral bonds rose, extending losses after data showed Italy, the bloc's third-largest economy, had unexpectedly slipped back into recession.
The ECB, which is due to meet on Thursday, has made unprecedented policy moves in recent months to try to keep the bloc's fragile recovery on track.
Portuguese bonds were the worst hit on Wednesday, their yields rising 10 bps to 3.79 percent. The country's main bourse dropped 4 percent to hit its lowest level in over a year, with financial stocks suffering over concerns about fallout from a rescue plan for ailing Banco Espirito Santo.
The benchmark 10-year U.S. Treasury note was up 6/32, the yield at 2.4618 percent.
The European Union and the United States last week adopted tough new sanctions against Russia over its actions in Ukraine, marking a new phase in the biggest confrontation between Moscow and the West since the Cold War.
Russian Prime Minister Dmitry Medvedev threatened on Tuesday to retaliate for the grounding of a subsidiary of national airline Aeroflot because of EU sanctions, with a newspaper reporting that European flights to Asia over Siberia could be banned.
Risk aversion and improving U.S. economic data, which continued on Wednesday with a narrowing of the trade deficit, helped lift the dollar index to as high as 81.716, an 11-month high against a basket of major currencies.
Oil prices bounced higher after industry data showed a large drop in U.S. crude stocks last week. Brent crude gained 68 cents to $105.29. U.S. crude gained 52 cents to $97.90. Brent settled on Tuesday at its lowest level since Nov. 7, while U.S. crude fell to its lowest level since early February. (Reporting by Chuck Mikolajczak; Editing by Dan Grebler)