Prospects for yuan appreciation fell to the lowest since the dollar peg was scrapped a year ago as an estimated 33 per cent drop in the trade surplus gives China room to rebuff US calls for faster gains, forwards contracts show. While US officials from Treasury Secretary Timothy F. Geithner to New York Senator Charles Schumer are seeking faster appreciation, the yuan\'s gains are slowing. The currency rose 1.9 per cent against the dollar in the first half of this year, down from its 2.9 per cent advance in the previous six months. Russia\'s rouble strengthened 9.4 per cent in the January-June period and Brazil\'s real advanced 5.9 per cent. Article continues below Dampening growth Smaller gains may cool global demand for Chinese assets as this year\'s three interest-rate increases damp growth in Asia\'s largest economy. So far in July, 12-month non-deliverable forwards have traded 1.3 per cent stronger than the yuan on average, the least since a two-year peg ended in June 2010, according to data compiled by Bloomberg. The government will say the trade surplus narrowed to a seven-year low of $37.2 billion in the first half, according to the median forecast in a survey of 21 economists ahead of data due tomorrow. \"Smaller surpluses support any claim from Beijing that the yuan is not so undervalued,\" said Joe Lau, a Hong Kong-based economist at Societe Generale SA. \"A controlled appreciation would help to ease the main problem of excess liquidity and also assist in raising incomes and domestic purchasing power.\" The yuan was little changed at 6.4648 per dollar, near a 17-year high of 6.4599 reached on July 4. Twelve-month forwards rose 0.1 per cent to 6.3848, a 1.3 per cent premium to the spot rate, based on data compiled by Bloomberg. Senator Schumer, a New York Democrat, plans to reintroduce legislation aimed at forcing China to raise the value of its currency, according to a letter to colleagues. Geithner said June 28 that China should continue moving \"over time\" toward an exchange-rate system that reflects market forces. China revises dates for data release China said it will bring forward the release of June inflation and producer prices data to today from July 15 as part of efforts to stop leaks. Consumer prices rose 6.2 per cent from a year earlier, the most since July 2008, according to the median forecast in a Bloomberg News survey of 19 economists.Producer prices may have climbed 6.9 per cent after a 6.8 per cent gain in May. The trade surplus may have fallen to $14.2 billion (Dh52.16 billion) from $20 billion a year earlier, according to the median estimate in a Bloomberg survey.