WASHINGTON — In an unusual move, the president of the Federal Reserve Bank of St. Louis released a paper Thursday warning that the Fed’s policy of keeping interest rates near zero during the economic crisis may lead to Japanese-like deflation in coming years.

Japan has been mired in a long economic slump with low growth and falling prices, or deflation. St. Louis Fed President James Bullard warned that absent more aggressive moves to spark its own slowing economy, the U.S. could be in for similar debilitating deflation. The Fed targets its benchmark interest rate at between zero and a quarter percentage point.

“Promising to remain at zero for a long time is a double-edged sword,” he warned, saying that the Fed’s effort to stimulate the economy that way may end up creating expectations for falling prices.

In deflation, asset prices fall, and a downward spiral takes hold, where businesses and consumers hoard cash on the assumption that prices will be lower soon. That leads to a stall in economic growth, or contraction, and jobs and income are lost in a vicious spiral down.

“The U.S. is closer to a Japanese-style outcome today than at any time in recent history,” Bullard wrote in his paper.

Bullard argues that by holding its benchmark lending rate near zero for more than 18 months, and by promising to do so indefinitely, the Fed has wet gunpowder. The effort may have failed to stimulate the economy sufficiently to power it forward, and public expectations for inflation may fall.

A better way to stimulate economic growth now, Bullard argued, is to have the Fed aggressively buy up government debt. Economists call this process quantitative easing; it has the effect of printing more money because it increases the money supply. That stimulates both inflation and expectations of future inflation.