Stocks are losing ground

Stocks opened little changed on Tuesday but quickly lost ground during the morning session, threatening to close lower for a second straight day.

At 11 a.m. ET, the Dow is down 104 points (0.56%), the S&P 500 is down 7 points (0.36%), and the Nasdaq is down 10 points (0.21%).

McDonald's shares are down 4%, the most on the Dow, after the company's earnings results showed that its turnaround strategy is losing steam.

US same-store sales grew 1.8% in the second quarter, following 5.4% growth in the prior quarter, and missing analysts' forecast for 3.2% growth.

Shares of 3M and Verizon were also lower after earnings. Caterpillar was up 1.7% after reporting second-quarter sales and profit that beat forecasts. The industrial behemoth cut its guidance for 2016 earnings and said it did not expect economic conditions to improve.

On the S&P 500, the telecom and utilities sectors were the biggest laggards.

Crude oil is lower, with West Texas Intermediate crude futures in New York down 1% to $42.67 per barrel. Oil has declined more than 10% in July amid fresh concerns about the bloated level of US inventories.