China and United States will hold talks on an investment treaty that could greatly widen opportunities for American companies in China.

The announcement came as the two countries wrapped up the fourth Strategic Economic Dialogue (SED), which began on the US Naval Academy campus in Annapolis on Tuesday.

Vice-Premier Wang Qishan and US Treasury Secretary Henry Paulson co-chaired the meeting as special representatives of President Hu Jintao and US President George W. Bush.

"This is a successful meeting," Wang said. The Chinese delegation was scheduled to meet with Bush and attend a joint closing news conference with Paulson at the Treasury Department.

Apart from widening the opportunities, the investment treaty will also make it easier for US companies to do business in China.

"The agreement will have very clear rules on the treatment of investors and the need to comply with those rules transparently and according to the rule of law," a US administration official said.

The official spoke on condition of anonymity because the formal announcement was to be made at the closing news conference.

The two countries are likely to announce other agreements in areas such as strengthening energy security, cutting global pollution and expanding food monitoring too.

Paulson hoped the discussions would produce enough results to persuade the next administration to continue the SED.

And in his opening speech on Tuesday, Wang said that "no matter what happens, it's necessary to continue using this important platform".

He urged both sides to move forward patiently as China implements the necessary reforms, and said the two countries should avoid "complicating and politicizing economic issues".

The twice-a-year discussions, alternating between China and the US, began in 2006.

The two-day talks were also attended by central bank governor Zhou Xiaochuan and US Federal Reserve Chairman Ben Bernanke.

Zhou said China is interested in learning from the regulatory mistakes of the US that led to the subprime mortgage crisis.

The two sides also shared their experiences and views on the current global economic and financial situation and bilateral economic and trade ties, and pledged to cooperate more intenselythrough the SED.

The fourth SED focused on five specific topics: financial and macro economic management, developing and protecting human capital, benefits of open market and trade, enhancing investment, and advancing joint opportunities for cooperation in energy and the environment.

China and the US were scheduled to sign a 10-year cooperation agreement on energy and environmental protection after the meeting.