TRADE Development Council economists hope that continuing economic recovery in the US will drive export growth this year, but they warn that a slowdown in China would damage Hong Kong trade. ''The US economy saw an upturn in the second half of last year. The outlook appears steady - perhaps three per cent growth,'' said TDC chief economist Edward Leung. He said the upswing in the US economy and better than expected Christmas sales in Europe had already boosted on-the-spot orders at trade fairs and exhibitions. At the 13th Electronics Fair last October, orders had been almost double those of 1992, he said. The Toys and Games Fair last month saw a 17 per cent increase in overseas buyers, said Mr Leung. That contributed to a 40 per cent increase in confirmed orders. China now accounts for nearly a third of Hong Kong's total exports, with half of that intended for mainland consumption, according to the TDC. Last year re-exports grew by 19 per cent to $823.22 billion while total exports rose by a more modest 13 per cent to $1.04 trillion, according to government figures. That means the territory now heavily depends on China's ''market dynamism,'' Mr Leung said. ''The health of the mainland economy will continue to impact strongly on Hong Kong's trade prospects.'' That meant growth might slow in the second half of the year if China again tightened credit controls, he warned. Computers and office equipment were expected to sell well in China this year, while consumer goods would also continue to sell, he said.