China, Canada, the Netherlands, Germany were assigned "AA +".
The United States and Saudi Arabia got an "AA" rating.
France , the United Kingdom, Korea and Japan got "AA-"s.
The countries that were assigned local currency sovereign credit rating of "A-" level include Belgium, Chile, Spain, South Africa, Malaysia, Estonia, Russia, Poland, Israel, Italy, Portugal and Brazil.
Dagong gave China's yuan-denominated debt an "AA-plus" rating with a stable outlook -- higher than Moody's "A1" and S&P's "A-plus" -- due to its rapid growth and relatively low debt. China's foreign currency rating was "AAA" in Dagong's report.
Guan Jianzhong, chairman of Dagong, said during a press conference in Beijing to introduce China's first sovereign credit rating report, that the current Western-led rating system "provides incorrect credit-rating information" and fails to reflect changing debt-repayment abilities.
"We want to make realistic and fair ratings and mark a new beginning for reforming the irrational international rating system," Guan said.
Dagong said it rated the 50 countries according to its own credit rating standards for the sovereign entity of a central government, which include "the ability to govern a country, economic power, financial ability, fiscal status and foreign reserve".
In the report, Dagong rated US government debt AA with a negative outlook, which was lower than the firm's top AAA rating. It warned that Washington, along with Britain, France and other countries, might have trouble raising more money if they let fiscal risks get out of control.
"The interest rate on debt instruments will go up rapidly and the default risk of these countries will grow even larger," the report said.Dagong was founded in 2007 and had published its rating procedures in 2009.