America's credit rating is once again at risk. 

Moody's Investors Service said Tuesday that it would probably cut its triple-A rating on U.S. government debt by a notch unless congressional leaders can strike a budget deal in the coming months to bring down the deficit. 

"If those negotiations lead to specific policies that produce a stabilization and then downward trend in the ratio of federal debt to GDP over the medium term, the rating will likely be affirmed," Moody's said in a press release Tuesday. "If those negotiations fail to produce such policies, however, Moody's would expect to lower the rating, probably to Aa1." 

The threat comes after one of the other big three ratings firms, Standard & Poor's, downgraded the U.S. last year following the brawl in Washington over the debt ceiling. 

The country is once again headed for a debt-ceiling showdown, with Moody's predicting the country will run up against the ceiling "around the end of this year." Any potential downgrade is not likely until at least next year.