Yields on 10-year US Treasury notes touched 2.332 percent, their lowest level since Feb. 27, after the disappointing March sales by major US automakers heightened concerns that America's long, robust boom car sales cycle may finally be losing steam.
"US auto sales raise questions about consumer demand, consumer spending going forward," said bond strategist Stan Shipley of Evercore ISI in New York. "And therefore, you're going to question how many times the Fed can tighten and how high can the 10-year yield rise."
Analysts also said investors' performance was reset for the second quarter, giving them an opportunity to either reduce short positions in Treasuries or sell stocks and reallocate into US debt. The benchmark US S&P 500 stock index was last down 0.2 percent.
Factors such as a less hawkish-than-expected Federal Reserve and reduced confidence in fiscal stimulus from President Donald Trump's administration motivated investors to shift into Treasuries, analysts said.
New York and other states challenged the Trump administration on Monday for illegally blocking energy efficiency standards, casting further doubt on the new government's ability to push through planned reforms.
Yields on three- and five-year Treasuries hit their lowest level since Feb. 28, at 1.448 percent and 1.863 percent, respectively, while seven-year yields hit their lowest level since Feb. 27, at 2.147 percent, and two-year yields touched a one-week low of 1.234 percent.
"Certainly the Trump-flation trade seems a lot more wobbly now," said Aaron Kohli, an interest rate strategist at BMO Capital Markets in New York. "There is no real reason to be aggressively maintaining a big short base in Treasuries."
Analysts said an explosion that tore through a train carriage in a St. Petersburg, Russia, metro tunnel in what authorities called a probable terrorist attack, killing 10 people, was another catalyst for the risk-off move into safe-haven US Treasuries.
US 30-year Treasury bonds were last up 25/32 in price to yield 2.978 percent, from a yield of 3.017 percent late Friday. US 10-year Treasury notes were up 14/32 in price to yield 2.344 percent, from a yield of 2.395 percent late Friday.