BEIJING (AP) -- The contraction in China's manufacturing worsened in March as the global downturn battered trade, data showed Wednesday, and President Hu Jintao said problems due to the crisis are growing as he left for a London economic summit.

The monthly purchasing managers index by brokerage CLSA Asia-Pacific Markets showed manufacturing shrank for an eighth month in March. Based on a survey of some 400 companies, the index fell to 44.8, down from February's 45.1, on a scale where numbers below 50 show activity is shrinking.

"Business conditions at Chinese manufacturers continued to deteriorate at a marked rate in March," Hong Kong-based CLSA said in a statement. It said companies cut more jobs as orders declined.

The data suggested China is still mired in a slump despite a huge government stimulus and optimistic statements by Premier Wen Jiabao and other officials. The central bank said last week the decline appeared to be slowing and data point to a recovery.

Manufacturing, which accounts for about 40 percent of China's economy, has been battered by a collapse in exports and weaker Chinese consumer sales. The government says 20 million migrant laborers have been thrown out of work, and communist leaders worry that further job losses could fuel unrest.

"China's economic difficulties are clearly increasing," Hu told the Xinhua News Agency in an interview before leaving for Thursday's meeting in London of leaders from the Group of 20 major economies to discuss the global crisis.

"This is mainly shown in declining trade, weakening industrial production, management difficulties in some industries and growing employment troubles," Hu said. He gave no new details on job losses.

Hu was expected to use the London summit to push China's demand for a bigger role in managing the world economy, including a more prominent place in the International Monetary Fund and other finance bodies.

On Tuesday, the Asian Development Bank cut its 2009 growth forecast for China and other developing Asian economies to 3.4 percent from 5.6 percent due to plunging trade. It said China should grow by 7 percent, down from last year's 9 percent.

Also Wednesday, a state newspaper reported that Beijing will send a trade mission to the United States this month ahead of the first meeting of a high-level U.S.-Chinese economic dialogue since President Barrack Obama took office.

The group will visit Washington, Chicago and San Francisco, the China Daily said. It gave no details of which industries might be represented or whether they might sign contracts to buy American goods.

The trip comes ahead of the U.S.-Chinese Strategic Economic Dialogue, a wide-ranging forum held twice a year to address trade and economic disputes. No date has been set but China has said Obama and Chinese President Hu Jintao will discuss the format during this week's G-20 summit in London on the global economic crisis. The last meeting was in December.

Beijing sent similar missions to the United States ahead of past rounds of the dialogue to buy jetliners and other goods in an effort to diffuse trade tensions.

In February, a 200-member delegation delegation of Chinese businesspeople and officials visited Europe and the government says it signed contracts worth more than $13 billion in Britain, Germany, Switzerland and Spain.

A second group followed in March to look at investment opportunities in auto manufacturing, textiles, chemicals, energy conservation and other areas.

Beijing has described the missions as an effort to expand trade at a time when the global financial crisis is fueling protectionist sentiment.