Asia's largest refiner Sinopec said its net profit for the first half year would decrease by over 50 percent from a year earlier, as it saw big losses in its oil refining business.

In the first half of 2007, Sinopec's net profit was 34.93 billion yuan.

"The gap between the high crude price on the international market and the relatively low price of refined oil products domestically has put the company's refining business in deeply red," the company said in a statement.