Concern that Spain could be the next European country to struggle with its debts drew traders into U.S. government bonds for a second day in a row.
The price of the 10-year Treasury note edged up 6.25 cents for every $100 invested. The yield was 1.98 percent, unchanged from late Friday.
The 10-year Treasury yield traded as low as 1.95 percent Monday, its lowest in more than a month, but then drifted slowly higher in the afternoon.
Borrowing costs for the Spanish government rose sharply on Monday, a sign of weaker confidence in the country's ability to repay its debts while its economy shrinks. The yield on the country's 10-year government bonds hit 6.10 percent, the highest since a new conservative government took office in December.
Throughout Europe's financial crisis, traders have responded to rising worries by buying Treasurys, which pushes U.S. interest rates down.
In other Treasury trading, the price of the 30-year bond was unchanged. Its yield ended the day at 3.13 percent, the same as it was late Friday. The yield on the 2-year note also remained at 0.27 percent.
In the market for short-term bills, the 3-month T-bill paid a yield of 0.08 percent.