Fitch warned today of a possible cut to the US AAA sovereign credit rating later this year if the ongoing government shutdown leads to it hitting its debt ceiling and hampering budget setting. 

"If this shutdown continues to March 1 and the debt ceiling becomes a problem several months later, we may need to start thinking about the policy framework, the inability to pass a budget and whether all of that is consistent with triple-A," Fitch's global head of sovereign ratings James McCormack said. 

"From a rating point of view it is the debt ceiling that is problematic," McCormack added.

A shutdown of about a quarter of the US government entered its 19th day today, with lawmakers and the White House divided over Republican President Donald Trump's demand for money for a border wall with Mexico.