Source: Sharecast
As of 1430 BST, the Dow Jones Industrial Average was down 0.34% at 40,526.76, while the S&P 500 lost 0.01% to 5,544.14 and the Nasdaq Composite came out the gate 0.20% weaker at 17,835.38.
The Dow opened 138.26 points lower on Friday, extending losses recorded in the previous session.
In focus on Friday, a major outage involving Microsoft and cybersecurity firm Crowdstrike led to systems crashing at businesses around the world, including airlines, banks and hospitals. Microsoft said on Thursday it was investigating issues with its cloud services in the Central US region, which had caused the grounding and cancellation of several flights. Reports emerged on Friday morning that a software update from Crowdstrike was causing Windows devices to crash, sending the shares 10% lower in early trading.
Elsewhere, presidential candidate Donald Trump told the Republican National Convention that he would enact "massive tax cuts" if he were to win the election in November, while Joe Biden was under pressure from fellow Democrats to bow out of the race.
In the corporate space, American Express and Halliburton quarterly shares were set to be published on Friday.
No major data points were scheduled for release.
Reporting by Iain Gilbert at Sharecast.com