US stocks opened lower as worries about the state of the global economy continued to rattle investors.
Shortly after trading began the Dow Jones was down 173.24 points, or 1.1%, at 16,106.85.
The S&P 500 index fell 16.71 points to 1,922.05, while the Nasdaq was 31.97 points lower at 4,720.78.
Shares in Caterpillar fell 7% after the construction and mining equipment maker warned of falling revenues and announced thousands of job cuts.
The company cut its forecast for revenues this year by $1bn to $48bn, adding that sales in 2016 would be about 5% lower.
Caterpillar – which has been hit by the downturn in the mining and energy sectors -also said it would cut up to 5,000 jobs by the end of 2016, and could shed 10,000 posts by 2018.
Later on Thursday, investors will be keeping a close eye on a speech being given by Federal Reserve chair Janet Yellen on inflation.