The S&P 500 was 0.9 percent lower in early trading after Moody’s Ratings became the last of the three major credit-rating agencies to say the US federal government no longer deserves a top-tier “Aaa” rating.

Investors will get the first chance to react to Moody’s downgrade of the U.S. credit rating late Friday over rising government debt and they’ll also look for more progress from President Trump on trade deals as the week kicks off.

Moody's downgrade of the U.S. sovereign credit rating has elicited mixed responses among Republicans in Congress, with some questioning the motive behind the change and others depicting it as a warning that lawmakers should heed as they wrestle with a sweeping tax and budget bill.

Moody’s Ratings downgraded the United States’ debt on Friday, stripping the country of its last perfect credit rating. The move could rattle financial markets and push up interest rates.Video above: Best money moves to make right now in a volatile ...