WASHINGTON — Janet L. Yellen, chairwoman of the Federal Reserve, said on Sunday that the American economy was in good health in an upbeat assessment that reinforced expectations the Fed is planning to raise its benchmark interest rate later this year.

Job growth is strong, companies are increasing investment, and the United States is benefiting from the improved health of the global economy, Ms. Yellen said in remarks to the Group of 30, which hosts gatherings of international policy makers and private-sector bankers.

Referring to the Fed’s benchmark rate, Ms. Yellen said, “We continue to expect that the ongoing strength of the economy will warrant gradual increases in that rate to sustain a healthy labor market and stabilize inflation around our 2 percent longer-run objective.”

The Fed has raised its benchmark interest rate twice this year, in March and in June, to a range between 1 percent and 1.25 percent. Investors expect a third 0.25 percentage point increase at the Fed’s final policy-making meeting of the year, in mid-December.