BANGKOK, Thailand — China's and India's plans to produce more biofuels could cause shortages of water, which is needed for crops to feed their growing populations, according to a water study released Thursday.

The International Water Management Institute study said both countries are counting on maize and sugarcane, which need large amounts of water, for much of their biofuels.

"Crop production for biofuels in China and India would likely jeopardize sustainable water use and thus affect irrigated production of food crops, including cereals and vegetables, which would then need to be imported in larger quantities," Charlotte de Fraiture, the study's lead author, said in a statement.

"Are these countries, particularly India which has devoted so much effort to achieving food security, adequately considering the trade-offs involved, especially the prospect of importing food to free up sufficient water and land for production of biofuel crops?"

Neither an Indian nor a Chinese government spokesman could immediately be reached for comment on the study, which follows one released earlier this week by the National Research Council.

The earlier study warned that increased production of these crops for ethanol could threaten water supplies in the United States.

The institute study is also the latest to warn that growing demand for biofuels could shortchange poorer countries that depend on staples like maize to feed their populations. Setting aside more land for biofuels could also raise prices for everything from eggs to beef, as feed would become more expensive.

"For the 2 billion poorest people in the world, many of whom spend half or more of their income on food, rising grain prices can quickly become life-threatening," Lester Brown, the founder of the Washington-based Earth Policy Institute think tank, wrote in 2006.

"The broader risk is that rising food prices could spread hunger and generate political instability in low-income countries that import grain," Brown wrote.

The institute study said China aims to increase biofuels production fourfold to around 4 billion gallons of ethanol — 9 percent of its projected gasoline demand — by 2020, from a 2002 level of 950 million gallons.

India is pursuing a similarly aggressive strategy. Earlier this week, its Cabinet approved a plan to require oil companies to sell gasoline with a blend of at least 10 percent ethanol by next year, or double current levels.

To meet their biofuels targets, China would need to produce 26 percent more maize and India 16 percent more sugarcane, the study found. It said doing so would require an extra 20 gallons of irrigation water per person per day in China, and an additional 18.5 gallons per day in India, beyond what is needed for food.

The institute 's David Molden said in a statement that the situation could worsen already dire water shortages in parts of China and India.

"Without major changes in water management, how are we going to feed a growing population, satisfy increasing demand for meat, and, on top of that, use crops as a major source of fuel?" Molden asked.