The head of the U.S. central bank says that with the country's improving economy an interest rate increase could be "appropriate relatively soon."

Federal Reserve Chair Janet Yellen, in prepared remarks ahead of a congressional hearing Thursday on the state of the U.S. economy, said central bank policy makers would only have to raise interest rates gradually in coming months if they decide to.

U.S. economic analysts are widely predicting a rate increase could be approved at the policy makers' last meeting of the year in mid-December. It would be a year after the Federal Reserve approved a quarter of a percentage point increase in its benchmark lending rate, its only rate increase since the country's steep recession in 2008 and 2009.

Since then, the world's largest economy has added 15 million jobs and the unemployment rate has been cut from 10 percent during the worst days of the plunging economy to 4.9 percent, a normal rate by U.S. standards.

But there is still economic angst through much of the U.S., even though it has the world's largest economy.  Many working class Americans in rural areas and small towns have felt left out by the country's recovery, much of it centered in large cities, and last week were a major force in the election of Republican Donald Trump as the country's new president, based on his promise to boost the American economy.

Trump has proposed a major increase in spending to fix the country's roads, bridges and airports -- and add jobs to make the repairs..