BOSTON (AP) — Federal Reserve Chairman Jerome Powell said Tuesday that he sees no need to drop the central bank's current gradual approach to raising interest rates.

Powell said the combination of steady, low inflation and very low unemployment shows the country is going through "extraordinary times."

The central bank is trying to make sure it doesn't raise rates too quickly and push the country into a recession, or move too slowly and set off higher inflation, he said. He added that the Fed's goal of gradual increases in interest rates is an effort to balance those risks and extend the current expansion, now the second longest in U.S. history.

Powell's comments, delivered to the annual conference of the National Association of Business Economics, came a week after the central bank approved a third quarter-point hike in its benchmark policy rate, pushing it to a level of 2 percent to 2.25 percent.

It marked the third rate hike this year and the eighth increase. The Fed began gradually raising rates in December 2015 after a period of seven years in which it kept its policy rate at a record low near zero to try to lift the economy out of a deep recession.

Powell noted in his speech that the unemployment rate stands near a 20-year low of 3.9 percent, while inflation has risen close to the Fed's 2 percent target for annual increases in inflation.

The Fed's economic forecast is in line with many others that show unemployment remaining below 4 percent through the end of 2020, with inflation staying near the 2 percent target over the same period, he said.

He was asked by a reporter at his press conference last week whether this forecast was too good to be true. He called that "a reasonable question" given that since 1950, the country has never experienced such a long period of low, stable inflation and very low unemployment for such an extended period.

He said it runs counter to an economic theory known as the "Phillips curve," which argues that low unemployment forces employers to push up wages to compete for scarce workers, triggering more inflation.

Powell said he did not think the Phillips curve is dead. But various changes in the economy, including better conduct of monetary policy by the Fed, had "greatly reduced, but not eliminated, the effects that tight labor markets have on inflation," he said.

He said these developments support the Fed's current cautious approach in raising interest rates even as unemployment keeps moving to lows not seen in 50 years. But he said there were risks to the Fed's current gradual approach to raising rate hikes. For that reason, central bank officials will be prepared quickly to change policy if conditions warrant such a change.