The Dow Jones Industrial Average fell 15.87 points, or 0.19%, to end at 8,539.73.
The tech-dominant Nasdaq gained 19.75 points, or 1.09%, to 1,827.47, while the broad-market Standard & Poor's 500 index advanced 2.86 points, or 0.31%, to 921.23.
All three key indices ended the week lower; the Dow by 3% per cent, the Nasdaq 1.7% and S&P 2.6 %. Nonetheless, the S&P 500 is up 36.2% from the closing low on 9 March.
In the absence of major earnings or economic reports on Friday, investors entered the market on the last trading day of the week boosted by data released on Thursday that indicated easing labour woes and signs of manufacturing recovery.
But their optimism fizzled out as they turned cautious ahead of the weekend, with oil and other commodity prices also weakening after shooting up earlier.
New York's main futures contract, light sweet crude for delivery in July, ended sharply lower at $US69.55 a barrel after climbing past $US72 dollars earlier amid political tensions in Iran and escalating turmoil in Nigeria.
Among active stocks was Microsoft, which surged 2.43% to $24.07 after analysts at Goldman Sachs recommended a buy for the software giant.
Apple rose 2.65% to $US139.48 dollars as the latest version of its iPhone went on sale.