WASHINGTON (AFP) - The US economy grew during May and June, keeping up momentum after the first quarter's stall, the Federal Reserve's Beige Book survey said Wednesday.

All 12 of the central bank's districts indicated that economic activity expanded, with growth characterised as "modest" or "moderate," according to the report, which will serve as a framework for the Fed's monetary policy meeting at the end of July.

Consumer spending, the driver that accounts for about two-thirds of US economic activity, revealed a mixed picture.

For some districts, low energy prices had helped boost spending. But in districts such as Minneapolis and Dallas, bordering Canada and Mexico, respectively, weaker spending was tied to the rising dollar, the report said.

Automobile sales increased in almost all districts, as did tourism, except for a further slowdown in New York, especially in New York City.

In the generally upbeat survey, people in Boston, Philadelphia, Atlanta, Kansas City and Dallas were "optimistic about future growth."

The report signalled some weaknesses, such as the stronger dollar that was curbing US exports.

The manufacturing sector had "uneven" activity in part due to the strong dollar and the slowdown in the oil and gas industry.

Employment increased or held steady in most sectors and wage pressures were described as "modest" in most districts.

At a Capitol Hill hearing on Wednesday, Fed chair Janet Yellen indicated the central bank saw the economy was strong enough to raise interest rates for the first time since 2006 later this year.

"If the economy evolves as we expect, economic conditions likely would make it appropriate at some point this year to raise the federal funds rate target, thereby beginning to normalize the stance of monetary policy," Yellen said.