Investors were focused on this week's annual central banking conference in Jackson Hole, Wyoming, which begins on Thursday, where Federal Reserve Chair Janet Yellen and European Central Bank President Mario Draghi are due to speak.

Draghi, who will also speak at an event in Germany on Wednesday, will be the main focus as investors watch for any indications that the ECB may begin paring asset purchases.

"Are they going to try to pare back asset purchases, what their thinking is on inflation," are among the main questions, said Subadra Rajappa, head of US interest rate strategy at Societe Generale in New York.

Yellen's speech on Friday will center on financial stability and is seen as less likely to provide clues on the Fed's balance sheet plans.

Many analysts and investors expect that the US central bank will announce a plan to reduce its balance sheet at its September meeting.

Treasury yields fell to almost two-month lows on Friday as personnel changes and discord in Washington reduced expectations that lawmakers will pass fiscal measures aimed at boosting growth.

US President Donald Trump on Friday fired his chief strategist Steve Bannon in the latest White House shake-up.

Many investors were seen as reluctant to buy Treasuries at relatively low yields, however, which kept a cap on the bond rally.

"Yields have refused to meaningfully rally," said Rajappa. "I think the market's resisting going mass long at these levels because everything looks very rich."

Benchmark 10-year notes were last up 2/32 in price to yield 2.19 percent, little changed from on Friday.