China said on Thursday that it opens its market to all investors, but foreign companies need to become more competitive to be successful.

Jiang Yu, a foreign ministry spokeswoman, said that the Chinese market has become increasingly competitive and foreign investors need to sharpen their competitive edge to better survive the market.

"Enterprises (of all countries) should get successful in the Chinese market through their competitive edge and strength," she said. "China provides a level playing field for all enterprises regarding issues of innovation, intellectual property rights and government procurement."

Her remarks came after US Commerce Secretary Gary Locke accused China of using investment barriers to block US investors on Wednesday, ahead of the bilateral Strategic and Economic Dialogue to be held next week.

Locke said in a speech that the US saw Chinese investment as a good thing for US businesses and workers but US companies operating in China are frequently shut out of entire industries, according to a Reuters' report.

Jiang said China will continue to improve its investment-related policies, abide by World Trade Organization rules and provide a stable, transparent and predictable environment for international investors.

Chinese experts said that the recent complaints of Locke and other US officials are largely a bargaining strategy ahead of the bilateral meeting scheduled for May 9 and 10, when the two are expected to exchange views on a series of crucial issues, such as the yuan's exchange rate policy and intellectual property rights protection.

"The complaints sound familiar; just as the old proverb goes, 'the squeaky wheel gets the oil', a well-used tactic by the US," said He Maochun, director of the Economy and Diplomacy Research Center at Tsinghua University.

He said the US is also putting pressure on China on trade and investment issues as a bargaining chip for the upcoming high-level meetings in Washington.

The US launched three anti-dumping and countervailing investigations on Chinese exports such as steel wire and steel wheels in late April and criticized China's intellectual property rights protection by placing China on a priority watch list.

But according to He, "The complaints are largely flawed, and Locke will attain a better understanding of the real situation during his upcoming tenure as the next ambassador to China."

"Actually Chinese companies have more complaints about the 'unbalanced' investment opportunities of investing in the US, but given the large size of bilateral trade and investment, frictions and complaints are normal, and cooperation will steadily go on," He said.

Locke also said the imbalance of opportunity is part of a broader trend of China recently narrowing its commercial environment after a long and fruitful period of opening.

However, the Commerce Minister Chen Deming, and other economic leaders, reiterated that China is maintaining openness as competition is the best impetus for development.