BERLIN, GERMANY - German Chancellor Angela Merkel hit out on Friday at the United States for not implementing internationally agreed rules on the amount of capital that banks have to hold, calling it "unfair."

"We negotiated Basel II (on capital requirement rules in 2004) together. When Basel II was introduced, the Americans simply didn't stick to it," Merkel said in a speech to a charitable foundation.

"This creates difficulties for us because things can be made more cheaply elsewhere. It is unfair," she said. "In September at the next G20 summit in Pittsburgh ... rules of the game like this have to be agreed upon."

Merkel said in a newspaper interview also published on Friday that slacker rules for banks in the United States meant that firms there found it easier to obtain credit than businesses in Europe.

"There is no fair competition between Europe and the United States," Merkel said in an interview with the Frankfurter Allgemeine (FAZ) daily. "Lending is key for future economic growth."

In the wake of the financial crisis when the banking system came close to collapse, world leaders pledged to tighten up the rules after a lack of proper regulation was blamed for allowing banks to take on excessive risks.