NEW YORK ( TheStreet) -- Don't even think about a September rate hike. The Federal Reserve won't raise interest rates until 2016, said Stifel Fixed Income's chief economist Lindsey Piegza.

"The Committee was very clear that they've recognized the under performance of the economy, talking about household spending still being very moderate and inflation still well below target," she said. "We expect this under performance to keep the Fed on the sideline much longer than the market expects into 2016."

But the Fed gave no clues on the timing of a rate hike in its statement Wednesday, following its two-day policy meeting, where it once again left short-term interest rates unchanged. Rates have remained near zero for over six years. 

"The Committee anticipates that it will be appropriate to raise the target range for the federal funds rate when it has seen some further improvement in the labor market and is reasonably confident that inflation will move back to its 2% objective over the medium term," the statement said.

Meanwhile, the decision to keep rates unchanged during its July meeting was unanimous, a dovish sign. "I think the 'some' language may have kept the hawkish members on board with this statement release, again not waiting for further improvement, but some further improvement," she said. "That may have quelled the concessions for the hawks."

The Fed also acknowledged that economic growth since the Fed's previous meeting in June "has been expanding moderately." 

However, central bankers will be watching the first reading on second-quarter gross domestic product, released Thursday morning.

The consensus estimate from Econoday suggests the economy grew 2.9% during the quarter. The Fed is expecting a rebound in economic growth after insisting first quarter's weakness was due to transitory factors, like cold weather.

"If we don't see 3% or 4% GDP in the latter six months of the year, the Fed really doesn't have a leg to stand on to justify a near-term rate hike," Piegza added.