A Chinese-government affiliate ratings agency, Moody's, Warren Buffett, and Federal Reserve Chairman Ben Bernanke all warned lawmakers and Obama on the looming US debt ceiling.

The Chinese ratings agency Dagong put the US on negative credit watch. 

If the raised limit fails to pass and the US faces default, the rating will be immediately and substantially downgraded, said CEO Guan Jianzhong.  (However, even if the debt ceiling is raised, the US still faces a downgrade, although not as soon, said Guan).

Moody's considers the probability of a default on interest payments to be low but no longer to be de minimis and has put the US AAA ratings on review for possible downgrade. 

Federal Reserve Chairman Ben Bernanke said the failure to raise the debt ceiling will have a very adverse effect very quickly on the recovery.

Billionaire investor Warren Buffett said the US shouldn't default on its debt because there is a big difference between a borrower who never defaulted (like the US currently) and a borrower who has (like the US threatens to be on August 2).

About the only person to indirectly support a default is legendary investor Stanley Druckenmiller, who in a WSJ interview said although a technical default (i.e. delaying payments for a short time) would be bad, it would be worse if the US government didn't fix its long-term budget deficit problem.

The US will default by August 2 if President Obama and Republican lawmakers don't agree to a deal to reduce the deficit and raise the debt ceiling.

The Republicans are refusing to raise taxes while Obama insists on them, hence their inability to agree on a deal.