A conference that convened here this week to address the fate of an ecologically threatened Central Asian basin the size of California has ended in stalemate between Kazakhstan and China, the two countries most reliant on its waters.

The heart of the basin is Lake Balkhash, the third-largest freshwater lake on earth, tucked in the southeastern corner of Kazakhstan. More than 20 percent of the country's population draws on the lake for its drinking water. Lumbering rivers flowing through neighboring Kyrgyzstan and China replenish the lake and adjacent wetlands.

After decades of water diversion to nearby factories and farms, Lake Balkhash is threatened with ''the same fate as the notorious Aral Sea,'' according to conference documents.

The Aral, in Kazakhstan and Uzbekistan, is widely considered one of the worst human-created ecological disasters in history. Rivers feeding the lake were diverted over decades for water-intensive cotton cultivation across Central Asia. That caused the sea to shrink drastically and eventually split into two anemic parts, devastating a once thriving fishing industry and causing deadly cancer clusters in nearby villages.

Progress at this week's conference, convened to introduce an environmentally sound economic development plan, stalled when China spurned Kazakhstan's proposal to send China large stocks of free or heavily subsidized food for 10 years in exchange for a commitment from China to allow an unimpeded flow of river water into Lake Balkhash.

''The Chinese were cautious and wary, but they also were listening,'' said Anna Bramwell, chief of operations for the European Union's political office in Kazakhstan, who attended the meeting.

As part of its ''Go West'' policy, China has offered incentives to people to move to its resource-rich Xinjiang territory, which includes part of the basin area. Chinese authorities have said the now sparsely populated region may eventually have as many as 40 million new inhabitants.

On top of population pressures, the water system is fast draining into nearby rice and sugar farms that consume twice the water that European and American operations require, according to representatives of the European Commission.

According to several participants in the conference, Kazakhstan's president, Nulsultan A Nazarbayev, strongly lobbied the other conference parties to urgently adopt preservation strategies.

But Mr. Nazarbayev has angered environmentalists in the past by appearing to endorse the building of a nuclear power plant in the basin, which yields more than 30,000 tons of fish a year and contains vast amounts of coal and building materials like marble.

Dr. Bramwell said, ''We're trying to move away from the classical environmental approach to a more win-win scenario where everyone has to pay for water and take responsibility for the damage'' they create.

Map of Kazakhstan highlighting Lake Balkhash: Lake Balkhash is imperiled after decades of water diversion.