* Risk-off buying helps Treasuries
* Yields back away from recent highs
* Gains break string of declines
By Michael Connor
NEW YORK, Feb 9 (Reuters) - U.S. Treasury debt prices rose on Monday as global investors sought shelter in safe-haven sovereign debt due to Greece's stand-off with the European Union and deadlier fighting in Ukraine.
After declines last week fueled by signs the Federal Reserve was near raising short-term rates fixed at near zero since December 2008, prices of long-term Treasuries favored by foreign buyers rose the most on Monday.
Wall Street stocks were weaker and yields on German bonds fell. Economic data showing a drop in China's imports and exports aggravated worries about global growth outside the United States, according to analysts.
"Concerns over the Greek situation, as well as Ukraine, have put a little anxiety into investors," said Kim Rupert, managing director of Action Economics in San Francisco. "It's a little bit more of a risk-off trade today."
Greek Prime Minister Alexis Tsipras on Sunday ruled out extending the country's bailout and said he would reverse some of the reforms imposed by its lenders, jeopardizing the country's finances and its place in the euro zone.
Nine Ukrainian troops were killed in the past 24 hours and seven civilians also died, Kiev said on Monday, when German Chancellor Angela Merkel was set to argue in Washington against arming Ukraine in its conflict against Russian-backed rebels.
Yields on benchmark 10-year notes touched a low of 1.886 percent on Monday and were last at 1.932 percent, reflecting a price rise of 2/32.
Thirty-year bond yields were last at 2.49 percent, reflecting a price rise of 20/32, after touching a session low of 2.464 percent, according to Thomson Reuters data.
Gains in Treasuries were likely limited by corporate bond sales from Microsoft and others, as well as Treasury auctions scheduled for this week, according to Rupert.
"Traders don't want to get the market too rich ahead of the auctions," she said. "We could see more concessions built into Treasuries once the auctions get underway tomorrow."
The Treasury department is scheduled to auction $24 billion of three-year notes on Tuesday, another $24 billion of 10-years on Wednesday and $16 billion of 30-years on Thursday.
But $80.6 billion of outstanding federal debt comes due this week for a net paydown of $16.6 billion. (Reporting By Michael Connor in New York; Editing by Chizu Nomiyama)