US Treasury yields fell to their lowest in nearly three weeks, drifting past significant technical levels, as fixed-income investors worried that President Donald Trump's pro-growth policies could be hamstrung by his focus on other issues.

Traders have worried that Trump's promises to cut corporate taxes and boost infrastructure spending have yet to be fleshed out and could fade further into the background or face more significant resistance with time.

Trump's nominee for Education Secretary, Betsy DeVos, was confirmed overnight in a contentious 50-50 vote by the US Senate, largely along party lines, that Vice President Mike Pence had to break by voting in favour.

Benchmark 10-year note yields fell to 2.37 per cent, their lowest since January 18, with other Treasury yields falling broadly to their weakest levels since mid-January. Prices on the 10-year were last up 6/32 to yield 2.39 per cent.

"The market is still giving the benefit of the doubt to the Trump administration, but the longer it takes for the market to see a real nexus on the policy front - those things that had expectations running high after the Republican sweep - the less convinced the market's going to be that Trump is going to really deliver on those," said Bruno Braizinha, interest rates strategist at Societe Generale.

Yields on the 10-year note fell below its 50-day moving average on Monday and continued to slip further past 2.40 per cent on Tuesday. That added to the downward pressure, giving the market a direction after a choppy early trading session, analysts said.

The yield on 2-year notes hit the lowest since January 17. They were last little changed in price to yield 1.17 per cent.

A solid 3-year note auction also helped increase buying, raising prices and pushing yields lower. The government sold $US24 billion worth of 3-year notes at a high yield of 1.423 per cent. The 3-year note was last yielding 1.416 per cent.

The one-month Treasury rate, two years forward, is now at 1.97 per cent, implying fewer than six 25 basis-point increases over the next two years. It had touched 2.30 per cent the day before the central bank raised rates in December. While the Fed's dot plot forecasts three rate increases this year, in 2016 the Fed raised the rate just once after having signalled four hikes.

Federal Reserve Bank of Minneapolis president Neel Kashkari overnight justified his vote last week to leave interest rates unchanged by saying inflation is in check.  

"While there are some signs of inflation slowly building toward our target, it isn't happening rapidly, and inflation expectations appear well-anchored," he wrote in an essay posted on the bank's website.

"With core inflation around 1.7 per cent, that suggests that the target range for the real federal funds rate is currently between -1.2 per cent and -0.95 per cent," Kashkari wrote. "Combined with a neutral rate of zero, that means monetary policy is currently about 100 basis points, or 1 per cent, accommodative. "

Kashkari said Fed policymakers have "extraordinarily powerful tools to deal with a surprise burst of inflation. We can always raise rates, quickly and aggressively if need be. And my view is that there is strong commitment among FOMC participants to maintaining our 2 percent inflation target.

"However, the closer we are to the zero lower bound, the fewer tools we have to deal with a surprise of low inflation or economic weakness. From a risk management perspective, that suggests, if we are to err, it is better to err on the side of being more accommodative than being more restrictive."

with Bloomberg