Traders said some investors were making room in their books before sales of $72 billion in new debt this week, including $32 billion in three-year notes on Tuesday, $24 billion in 10-year notes on Wednesday and $16 billion in 30-year bonds on Thursday.

Others, though, were buying Treasuries as a safe haven.

 In the United States, a deal is yet to be reached to avoid the so-called "sequestration" spending cuts that would enter into force next month if no deal is reached on raising the debt limit.

Investors will watch President Barack Obama's State of the Union speech later on Tuesday for clues on whether Republicans and Democrats can reach a budget compromise any time soon.

In Spain, investors fear a corruption scandal surrounding the ruling party could hit the government's already falling popularity ratings and hurt its ability to enforce further structural reforms.

In Italy, the rise in opinion polls of former Prime Minister Silvio Berlusconi's party ahead of this month's election raises concerns of a fragmented parliament that could hinder the reform efforts of the next government.

US benchmark 10-year T-note yields were 0.7 basis points higher on the day at 1.9716 percent, while T-note futures were 4/32 lower at 131-17/32.

"Everybody is concerned by the sequestration and they will be looking for any clues on that in the State of the Union," said Philip Marey, strategist at Rabobank. "Also there's this scandal in Spain and the elections in Italy," he said about the factors keeping US bonds well bid before the debt sales.

Lloyds strategists said the three-year debt auction on Tuesday should see strong demand due to "core yields trading towards the top end of the range, coupled with coupons and redemptions totaling $97.7 billion this week and ongoing uncertainty around peripheral countries."

Treasuries shrugged off news that North Korea had conducted a nuclear test as Pyongyang had said last month it was going to carry it out.