Traders flocked to a sale of 10-year Treasury notes, carrying on a big day for global government debt despite persistent worries over sovereign defaults.

A $21 billion reopening of the U.S. government's benchmark issue drew a high yield of 3.388 percent, just a shade above where the note traded before the auction results were released at 1 pm.

Moreover, the bid-to-cover ratio was a robust 3.30, representing the amount of money bid for each dollar auctioned. Foreign demand, as measured through the indirect bid, was a solid 54 percent.

Treasury yields had been higher during the day, but slipped following the auction as prices cut their earlier losses.

The 10-year notes last were off 7/32 in price, their yields at 3.37 percent from 3.34 percent late Tuesday and up from 3.30 percent on Monday.

The successful US auction came on the heels of a better-than-expected sale of Portuguese debt as that European Union nation battles default fears.

This week's auctions conclude with a $13 billion reopening of 30-year bonds on Thursday.

Yields rose for the second consecutive trading session in preparation for the new supply, which analysts expected to see good demand near current levels.

"I think at these levels it will be ok," said Michael Cloherty, head of rates strategy at RBC Capital Markets in New York.

Strong demand in Portugal's closely watched debt auction helped to ease concerns over the region, though analysts warned that jitters could resurface as peripheral countries face significant funding needs this year.

"There is a lot more issuance that needs to get done, this was the first of many," said Cloherty.

Spain and Italy will both issue bonds on Thursday, which analysts expect will go without a major hitch, though the countries could face elevated costs on the debt.

Treasurys pared some losses after a strong sale of 3-year notes on Tuesday, though the rally faded as people built premium into yields for this afternoon's auction, said Jim Vogel, interest rate strategist at FTN Financial in Memphis, Tennessee.

"Real money investors were slow to respond to the lower yields that we had on the 10-year in the low 3.30 percent area," he said. "That by itself is a good signal that the auction needs to be in the low 3.40 percent area in order to be well placed."

The notes traded Wednesday morning with yields of 3.42 percent in the "when-issued" market which indicates where traders expect the new debt will price.

Government debt prices also tend to dip ahead of the auctions as dealers short Treasurys to prepare for the sale before buying back the debt in the auctions.

Thirty-year bonds last dropped 28/32 in price to yield 4.55 percent, up from 4.49 percent on Tuesday. Five-year notes last dropped 10/32 in price to yield 2.03 percent, up from 1.96 percent on Tuesday.

The yield gap between 2-year note yields and 30-year bond yields also stayed near their record highs Wednesday, and the steepness of the yield curve may be supportive for Thursday's long bond auction, said FTN's Vogel.

"The 30-year is the one point on the curve that didn't really rally after payrolls," he said. "So it's not going to be as sensitive as it normally would be to the success or failure of the 10-year auction. It's got a bit of cushion."

The Federal Reserve will also announce details of its next round of purchases as part of its $600 billion bond buying program later Wednesday.

Credit Suisse analysts said in a report they expect the Fed will purchase $105 billion in aggregate for the period from mid-January to mid-February.