March 6 (Reuters) - Wall Street's main indexes opened

lower on Thursday as uncertainty about a trade war unleashed by

U.S. tariffs clouded sentiment, while chip stocks slid after

Marvell's forecast fanned worries of slowing demand for AI

infrastructure.

The Dow Jones Industrial Average fell 158.1 points,

or 0.37%, at the open to 42,848.49. The S&P 500 fell 56.8

points, or 0.97%, to 5,785.87​, while the Nasdaq Composite

dropped 348.2 points, or 1.88%, to 18,204.528.