BEIJING, Sept. 28 (Xinhua) -- The central parity rate of the Renminbi (RMB) against the U.S. dollar hit a new high Thursday, breaking the 7.90 mark.

    The yuan's value rose to 7.8998 for one U.S. dollar, bringing the currency's total appreciation to more than 2.66 percent since reform of the RMB exchange rate system began in July last year.

    This is the fifth new high in the past nine days, with the RMB exchange rate edging up from 7.94 to 7.93 and on to 7.92, 7.91 and 7.90.

    Last July, China pegged the yuan to a basket of currencies instead of just the U.S. dollar, allowing the currency to fluctuate within a daily 0.3 percent band from the central parity rate.

    Observers said China's huge trade surplus has pushed the yuan's value to new highs.

    China's trade surplus hit a monthly high of 18.8 billion U.S. dollars in August, with exports rising 32.8 percent to 90.77 billion U.S. dollars.

    Meanwhile, U.S. senators Charles Schumer and Lindsay Graham said Tuesday they had agreed to hold over a senate vote on tariff sanctions until the end of this week to give the government more time to negotiate with China.

    They made the decision after meeting with U.S. Treasury Secretary Henry Paulson, who has just returned from a trip to China.

    The two senators had threatened to force a vote in late September to impose a 27.5 percent punitive tariff on Chinese imports if the yuan is not revalued.

    U.S. critics argued that China's currency is undervalued by as much as 40 percent, giving Chinese goods price advantages and resulting in a mounting trade deficit for the U.S.

    The senators' action has increased pressure on the RMB, observers said. Enditem