US 30-year yields dropped to one-month lows, while those on two-year and 10-year notes slid to one-week troughs.

"This is partially from an equity sell-off that has been a little bit of a risk-off trade," said Ellis Phifer, fixed-income strategist at Raymond James in Memphis, Tennessee.

"We have the China trade talks, but we haven't really seen success at this point. Suddenly the bond market is taking its clues from that."

US President Donald Trump said on Thursday he did not plan to meet with Chinese President Xi Jinping before a March 1 deadline set by the two countries to achieve a trade deal.

A person briefed on the talks said Trump's advisers were concerned that accepting a meeting invitation at this stage would raise unfounded expectations for a quick deal and erode US leverage in the talks, where the two sides remain far apart on core structural intellectual property issues.

In mid-morning trading, US 10-year note yields fell to 2.635 percent, from 2.654 percent late on Thursday.

US 30-year bond yields were also down, at 2.985 percent , from 3.006 percent on Thursday. Thirty-year yields earlier fell to a one-month low of 2.976 percent.

On the short end of the curve, US 2-year yields slipped to 2.458 percent, compared with Thursday's 2.479 percent .

Jim Vogel, interest rates strategist at FTN Financial in Memphis, noted that this week's steady decline in yields is not being accompanied by widespread buying support.

"That missing ingredient leaves bond prices vulnerable to a gap higher on either a news jolt or a cumulative run of data that don't meet expectations. A thin rally usually invites profit-taking, but bears can't find momentum for falling bond prices either," Vogel said.

US yields were also tracking those on Germany's 10-year government bonds, which dropped below 0.1 percent for the first time since late 2016 on Friday, reflecting concerns about economic conditions in the euro zone's largest economy.

The 10-year Bund yield fell as low as 0.097 percent , dragging French and Dutch yields to their lowest levels in more than two years.