TREASURIES-Prices jump as Ukraine worries deepen

* NATO says Russian troops massing at Ukraine border

* Ten-year yield at lows not seen since May

* U.S. yields beckon

By Michael Connor

NEW YORK, Aug 6 (Reuters) - U.S. Treasuries prices shot up on Wednesday as tensions over Ukraine sapped global financial markets and left 10-year Treasury note yields at lows not seen since May.

Benchmark 10-year notes, which had traded above 2.50 percent on Tuesday, were off 10/32 in price to yield 2.44 percent. That is a level last seen on May 28, according to Reuters data.

Thirty-year Treasury bonds were up 22/32 in price to yield 3.24 percent after touching a yield high on Tuesday of 3.33 percent during trading shaped by bullish U.S. economic data.

Investor (Other OTC: IVSBF - news) concerns about the timing of Federal Reserve interest-rate hikes were receding, with fat differentials between European and U.S. yields proving increasingly alluring, portfolio managers said.

"The market is not so much, 'Oh my God, the Fed will be raising rates soon.' That is now off the table for a while," said Wilmer Stith, co-manager of the Wilmington Broad Market Bond fund in Baltimore, Maryland.

"Russia possibly being more aggressive over Ukraine is now on the table," Stith said. "U.S. Treasuries are very attractive on a yield basis with German 10-year bonds at 1.1 percent and ours now at 2.44."

After NATO said Russian troops were massing near Ukraine's border, European stocks fell 1.4 percent, while MSCI (NYSE: MSCI - news) 's world equity index was down 0.5 percent. Wall Street opened down.

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.

(Reporting By Michael Connor in New York; Editing by Nick Zieminski)