Chinese currency, the yuan, weakened 19 basis points Friday to 6.6341 per U.S. dollar, according to the China Foreign Exchange Trading system.

The central parity rate of the currency, also known as the renminbi (RMB), hit an all-time high of 6.6215 per dollar Tuesday to start 2011.

China's central bank announced on June 19, 2010, it would further reform the yuan exchange rate formation mechanism to improve its flexibility.

On China's foreign exchange spot market, the yuan can rise or fall 0.5 percent from the central parity rate each trading day.

The central parity rate of the RMB against the U.S. dollar is based on a weighted average of enquired prices from all market makers before the opening of the market each business day.