The Federal Reserve has stuck to its plan to keep stimulating the US economy until the job market improves and repeated its vow to keep rates near zero until mid-2015.

In a policy statement after a two-day meeting, the central bank acknowledged hints of strength in the US housing market, but reiterated a pledge to continue supporting growth even as the recovery picks up.

It said it would continue purchasing $40 billion in mortgage-backed debt per month to push interest rates lower.

The Fed did refer to a recent increase in inflation but said it was linked to higher energy prices, adding that inflation expectations have remained stable.

It also noted household spending has grown "a bit more quickly" but cautioned that business investment was softening.

"The Committee remains concerned that, without sufficient policy accommodation, economic growth might not be strong enough to generate sustained improvement in labour market conditions," the Federal Open Market Committee's statement said.

The Fed, which has held rates close to zero since December 2008, had already bought $2.3 trillion in mortgage-related and government debt before it launched its latest round of stimulus.

Some analysts have expressed concern the Fed's policies could spark inflation, but prices increases have remained tame so far.

Growth, however, has also remained tame.

US gross domestic product grew at an annual rate of just 1.3 percent in the second quarter.

Economists expect the pace of recovery quickened a bit in the second quarter but not by enough to put steady downward pressure on the jobless rate.

The Fed is expected to re-evaluate the extent of its monthly bond purchases at its December meeting.

In addition to its program to buy mortgage-backed debt, the Fed has been using proceeds from short-term government securities to buy longer-term ones.

That program, known as Operation Twist, expires at the end of the year.