China pledged Wednesday to buy rice from Thailand's growing mountain of unsold stocks, during a visit by Premier Wen Jiabao, officials said.

The memorandum of understanding, which did not specify the size or value of the exports, was part of an agreement between Wen and his Thai counterpart Yingluck Shinawatra to expand economic ties between the two countries.

"There's no precise timeframe or quantity because China did not want to be specific," said Thai government spokesman Tosaporn Sererak.

As a first step, 10 Chinese companies signed eight contracts to buy a total of 260,000 tonnes of rice, he said.

A controversial scheme introduced by Yingluck to boost farmer incomes has hit the competitiveness of Thai rice shipments.

The kingdom, which is set to lose its rank as the world's top rice exporter this year, produces about 20 million tonnes of the grain annually on average, about half of which is normally sold overseas.

This year, however, exports are expected to reach only about 6.5 million tonnes, according to the US Department of Agriculture.

The government says it is confident it can find buyers on world markets at a price that will raise the living standards of its farmers.

During Wen's visit, Thailand also invited Chinese investors to participate in projects including the Dawei deep sea port being jointly developed with Myanmar as well as in areas such as rubber processing, flood prevention and high-speed rail.