Bill Gross said demand for U.S. government debt may fall as energy-producing countries cut back on purchases after an almost 50 percent decline in oil prices.

“Not only can they not buy Treasurys with the excess but they may have to use their surplus in order to continue the budgets they’ve maintained because of $100 oil,” Gross, who joined Janus Capital Group Inc. in September, said in a Bloomberg Radio interview with Tom Keene.

Still, lower oil prices means lower inflation, a positive for the bond market, he said.

Gross, the former manager of the world’s largest bond fund at Pacific Investment Management Co., has called for negative returns for many asset classes this year. With oil prices under $50 a barrel and global economic growth sputtering after years of interest rates near zero, the Federal Reserve is constrained from boosting borrowing costs, according to Gross.

Investors will eventually seek alternatives to risky assets as they realize they’re paid too little for too much risk, Gross wrote in an investment outlook last week. They should hold high- quality assets with stable cash flows such as Treasurys, high-grade corporate bonds, and stocks of companies with little debt and attractive dividends, he said.

The $1.4 billion Janus Global Unconstrained Bond Fund, run by Gross since Oct. 6, has lost 0.8 percent in the past three months, trailing 51 percent of comparable funds, according to data from Chicago-based research firm Morningstar Inc.

Treasurys are off to the best start to a year since 1998 as tumbling oil prices lower the outlook for inflation and combine with record-low global sovereign yields to bolster demand for U.S. debt. The yield on the 10-year note fell below 2 percent for the first time since October last week as a report showing a drop in U.S. wages dimmed prospects for an early 2015 Fed rate increase.

With yields on German 10-year bunds, the euro area’s benchmark, at 0.495 percent, “it’s hard for a U.S. Treasury to move much higher, despite any employment report,” Gross said.