Wall Street opens flat as Janet Yellen's speech awaited

Wall Street opened little changed on Friday as cautious investors braced for a speech by Federal Reserve Chair Janet Yellen for clues on the timing of a US interest rate hike.

Yellen is due to speak at an event hosted by Harvard University at 1:15 pm ET. Her speech comes after a number of Fed policymakers this week struck hawkish tones on the trajectory of interest rates.

Investors have grown more comfortable with expectations that the central bank could raise rates as soon as June, with many taking the view that such a hike would reflect improvement in the country's economy.

A rate hike in June was seen as highly unlikely until recently. However, the Fed funds futures are now pricing in a 25% chance of a rate hike in June and 45% in July after a string of strong data and comments from policymakers.

The Fed next meets on June 14-15.

"We're expecting a lot of major data in the next few weeks and Yellen will balance her comments keeping that in view," said Nadia Lovell, US equity specialist at J.P. Morgan Private Bank in New York.

"Our view is that we will get two rate hikes this year. June doesn't seem likely with the British referendum but with housing data coming in strong and unemployment continuing to improve, July seems likely, with another one post-election in December."

At 9:34 a.m. ET the Dow Jones industrial average was up 19.66 points, or 0.11%, at 17,847.95, the S&P 500 index was up 2.6 points, or 0.12%, at 2,092.7 and the Nasdaq composite index was up 4.52 points, or 0.09%, at 4,906.29.

Eight of the 10 major S&P sectors were higher, with the consumer discretionary index's 0.30% rise leading the advance.

Data on Friday showed the US economic growth slowed in the first quarter although not as sharply as initially thought.

Gross domestic product rose at a 0.8% annual rate as opposed to the 0.5% pace reported last month - the slowest growth since the first quarter of 2015. Economists polled by Reuters expected a 0.9% growth rate.

The University of Michigan's final consumer sentiment index likely cooled a bit to 95.4 in May from a preliminary reading of 95.8 earlier this month. That data is expected at 10 a.m. ET.

Wall Street closed mostly flat on Thursday as investors took a breather following two days of strong gains.

Cyber security firm Palo Alto's shares were down 9.9% at $133.68 after posting a wider-than-expected quarterly loss.

GameStop fell 4.3% to $28.65 after the video-game retailer forecast lower-than-expected revenue and profit for the current quarter.

Ulta Salon Cosmetics and Fragrance was up 7.9% at $230.58 after the beauty product retailer raised its full-year forecast.

Advancing issues outnumbered decliners on the NYSE by 1,390 to 1,131. On the Nasdaq, 1,121 issues rose and 942 fell.

The S&P 500 index showed 10 new 52-week highs and no new lows, while the Nasdaq recorded 21 new highs and two new lows.