Investors worried about the US debt pile are weighing the House vote to approve President Trump's "big, beautiful" tax bill.

The Dow closed lower by 817 points, or 1.91%. The broader S&P 500 slid 1.61% and the tech-heavy Nasdaq Composite fell 1.41%. The three major indexes each posted their worst day in one month.

U.S. stock index futures were muted on Friday as investors were risk-averse after President Donald Trump's tax and spending bill won a crucial House vote the previous day, raising concerns about the country's deteriorating fiscal outlook.