China remains open to foreign investment and is keen to address key issues including the trade imbalance and food security, Vice-Premier Wu Yi said in Beijing on Friday in her keynote speech to American companies operating in China.

China and the US are major trade partners for each other, Wu said at an annual event at the American Chamber of Commerce in China.

Her speech came ahead of the third China-US Strategic Economic Dialogue, when top officials from the two countries will meet in Beijing early next month to discuss trade issues.

Trade between China and the United States has been developing very fast over the past decade, Wu said, and the two countries are now each other's second-largest trading partner.

Bilateral trade has grown from $2.5 billion in 1979 to $262.7 billion last year, she said. It is expected to surpass $300 billion this year.

In the past 10 years, the value of US exports to China has almost tripled, she said. China this year became the third-largest export market for US products.

Meanwhile, US companies doing business in China are making healthy profits, Wu said.

According to figures from AmCham, in 2006, investment by US companies in China was $80 billion, from which they made a total profit of $10 billion. More than 70 percent of all US firms investing in China are making profits, much of which comes directly from the Chinese market, she said.

In terms of investment, the US remains the largest source of foreign direct investment to China, with the total this year reaching $55 billion.

More than 200 US firms have set up research and development centers here, while China's investment in the United States is also increasing, especially in the industrial, technological, financial and insurance sectors.

China is also keen to address the challenges and problems of foreign trade, with one of the key issues being the provision of better protection for intellectual property rights, Wu said.

"IPR protection is not about anyone else; it is about China's own development," she said.

Wu also tried to ease worries by foreign companies that China is limiting investment in key industries in what they believe is "a violation of its free-trade pledges".

"Some American friends are worrying about whether China will shrink its opening-up policy and change its attitude toward foreign capital. The position of the Chinese government to value FDI (foreign direct investment) and attract more foreign capital won't change," she said, prompting loud applause.

"China's door will be open forever."

AmCham-China is a nonprofit business association, which represents more than 2,500 members and some 1,000 US companies in China.