NEW YORK: US Treasury yields fell on Tuesday as a decline in stocks boosted demand for the safe haven US debt, and before the United States government will sell $108 billion in coupon-bearing supply this week.

The Nasdaq tumbled more than 3% at the open on Tuesday as investors sold off shares of Tesla and other tech heavyweights, while simmering US-China tensions and concerns over a rocky economic rebound also weighed on sentiment.

That boosted demand for Treasuries, even though heavy supply this week is expected to weigh on the bonds.

"We have equity market weakness this morning, so it's probably neutralizing the set up (for the auctions)," said Tom Simons, a money market economist at Jefferies in New York.

Benchmark 10-year note yields fell 5 basis points to 0.674%. The yield curve between two-year and 10-year notes flattened 5 basis points to 52 basis points.

The Treasury Department will sell a record $50 billion in three-year notes on Tuesday, followed by $35 billion in 10-year notes on Wednesday and $23 billion in 30-year bonds on Thursday.

Demand for the longer-dated debt will be under scrutiny, after the government saw tepid interest in record large sales of the 10-year and 30-year debt in August.

"Those auctions were pretty sloppy, even after a pretty significant concession coming into them," said Simons. "The big sizes seem to be more significant and more difficult for the market to take down in the long end of the curve."

The government has been increasing Treasury supply across the curve as it pays for stimulus meant to blunt the economic impact of the novel coronavirus.

Investors will be watching to see if the US Congress is likely to pass additional spending as lawmakers begin returning to Washington this week.