US open: Stocks flat as investors await Yellen's testimony

Just before 10:00 in New York, the Dow Jones Industrial Average was up 0.15%, while the S&P 500 and the Nasdaq slipped 0.03% and 0.29% respectively.

Investors’ focus will be firmly on Yellen's remarks on monetary policy to gauge if the Fed is still on track to raise short-term interest rates this summer.

“There are factions in the US that are almost rabid for an interest rate hike, despite a string of poor data causing a dovish tone in the Fed’s last minutes release,” said Spreadex analyst Connor Campbell.

“Nearly every new figure in the US at the moment is then used as a tool in the discussion surrounding interest rates, so the markets will be waiting with bated breath to see which way Fed chair Yellen will lean.”

Meanwhile, the S&P/Case-Shiller composite index of home prices in 20 cities increased rose 4.5% year-on-year in December, exceeding expectations for a 4.3% rise.

In company news, cable television operator Comcast edged 0.3% higher after reporting better-than-expected fourth-quarter profits, driven by strong revenue gains at its high-speed internet, advertising and business services divisions.

Retail giant Home Depot rose 4.4% after reporting a 36% rise in fourth-quarter profit and said it would buy back $18bn of shares, despite warning that currency headwinds will impact 2015 earnings.

SunPower and First Solar jumped 16.9% and 13.7% respectively after saying late on Monday they planned an initial public offering for a pooled-asset spin-off.

Gold futures were down 0.3%, while the dollar rose 0.5% against the yen and 0.1 and 0.2% against the euro and the pound respectively.

After a sharp drop on Monday which led to speculations of an OPEC emergency meeting, oil prices rebounded, with Brent crude gaining 1.5% to just under $60 a barrel, while West Texas Intermediate rose 0.9% and was trading at $49.9 a barrel.