WASHINGTON - China has been concerned over Chinese firms' access to the US market and US restrictions on high-tech product exports, Chinese delegates attending the fifth China-US Strategic and Economic Dialogue (S&ED) said Wednesday.

The two countries held a special session on expanding bilateral trade and investment on Wednesday under the framework of the fifth S&ED.

At the special session, Chinese delegates warned against protectionism, noting that economic issues should not be politicized.

The Chinese side said as both China and the United States are undergoing economic transition, there are more opportunities than challenges in terms of economic cooperation.

China welcomes US investment and will continue to open up it market, especially the service sector, said Chinese delegates.

They expected the US side to ensure a level playing field for all Chinese companies, including State-run enterprises, in the United States.

China and the United States have been holding S&ED talks annually since 2009 as a major channel to enhance mutual trust, boost cooperation and properly handle differences.

The S&ED mechanism was upgraded from the former Strategic Dialogue and biennial Strategic Economic Dialogue, which were initiated in 2005 and 2006 respectively.