A key measure of the American economy slipped this month after three consecutive months of increases as consumers saw the trade war with China as an increased risk.

The Conference Board's consumer confidence index declined to 121.5 in June, the business research group said on Tuesday. The drop was more than the decline to 131.1 that economists surveyed by Reuters expected.

In May, the Conference Board reported a preliminary reading of 134.1 for the index, but revised last month's number to 131.3 in the latest report.

The drop brought the index to its lowest level since September 2017.