Wall Street is on edge about American investments again after receiving a significant warning about the safest of all safe havens: US debt.

Investors sold stocks and bonds after Moody’s downgraded the U.S. credit rating, potentially complicating negotiations around Republicans’ tax plan.

Moody's on Monday downgraded the long-term ratings of top American lenders such as JPMorgan Chase , Bank of America and Wells Fargo , after pushing the U.S. out of top triple-A rating club over its burgeoning $36 trillion debt.

U.S. stocks open lower after Moody's stripped the U.S. of its top credit rating. Treasury yields jump as investors demand more payout to hold US debt.

Investors sold U.S. government bonds and the dollar on Monday amid concerns about the U.S. fiscal picture. Stocks edged higher.

The downgrade follows a change in the outlook on the sovereign in 2023 due to wider fiscal deficit and higher interest payments, and comes as Congress debates tax and spending plans that could deepen the fiscal hole.

American markets fell to open the week Monday, reacting to Saturday's news that Moody's Ratings was downgrading U.S. debt.