The Thai company set to build Laos’s Xayaburi hydropower dam will not begin construction until a study determines the dam’s environmental effects on the Mekong River, Thai Prime Minister Yingluck Shinawatra said on Friday.

Yingluck reaffirmed her commitment to the study, which Mekong River Commission countries Cambodia, Laos, Thailand and Vietnam agreed in December to undertake before construction could begin.

“We will study together the scope of the impact along the Mekong and we will see what the impact is,” Yingluck said after a meeting with Prime Minister Hun Sen in Siem Reap.

Vietnam and Cambodia have voiced concerns over the effects the dam could have on communities downstream, following recent reports Thai development firm Ch.Karnchang has stepped up construction.

Hun Sen said he had voiced such concerns with Yingluck, whose country will receive 95 per cent of the dam’s electricity.

“Her Excellency, Yingluck, has affirmed that the dam has not been built,” he said. “We were very happy with this information and hope this will benefit both the upper and lower Mekong countries.”

Despite reports in April that Ch.Karnchang had signed a construction deal dated in March, Laos claims that only preliminary work has begun on the 1,260 megawatt dam.

Te Navuth, secretary-general of the Cambodan National Mekong Committee, said yesterday Cambodia’s ambassador in Vientiane had been invited to inspect the Xayaburi site today and tomorrow.

“But I don’t know [if he will attend],” he said.

Navuth said Cambodia and Vietnam would continue drafting a letter to the Lao government asking it to halt work.

Laos Foreign Minister Thongloun Sisolouth said on Friday preliminary work was on hold.

“The Lao government decided to postpone it. We have to do further studies,” he said, according to Reuters.

Ame Trandem, Southeast Asia program director of International Rivers, said it was vital the trans-boundary impacts were explored.

“The company has never looked at the impact on Cambodia,” she said, adding the project seriously threatened Cambodian fish stocks.

Ch.Karnchang could not be reached.

To contact the reporters on this story: Cheang Sokha at [email protected]

Shane Worrell at [email protected]