(Reuters) - Wall Street's main indexes opened lower on Wednesday, as investors awaited the outcome of a pivotal debate around U.S. President Donald Trump's tax-cut bill that has fanned concerns about the country's growing debt.

The Dow Jones Industrial Average fell 322.8 points, or 0.76%, at the open to 42,354.46. The S&P 500 fell 30.3 points, or 0.51%, at the open to 5,910.18​, while the Nasdaq Composite dropped 139.8 points, or 0.73%, to 19,002.942 at the opening bell.

(Reporting by Kanchana Chakravarty in Bengaluru; Editing by Devika Syamnath)