China has offered Bangladesh "real-time data" on the upstream water flow of one of South Asia's biggest rivers in an attempt to help forecast floods in the delta nation, an official said.

"We have signed an agreement with China on sharing (data on) the water flow of the Brahmaputra which originates in China and flows entirely through Bangladesh," said Tauhidul Anwar Khan, a member of Bangladesh's Joint Rivers Commission.

"It is a big step for us to monitor the water flows of the river as the Brahmaputra contributes some 67 percent of the country's river waters and is the chief reason behind floods in the past," he said.

Under the deal, China will share data on the river's water level, rainfall in the river basin and river discharge in the north as it flows to Bangladesh via India from April 15 this year, he added.

Bangladesh gets data on the water levels of the Ganges and some other important rivers that flow from India during the rainy season but the government said it was not sufficient to make forecasts of possible floods in the country.

"The data we get from India give us only four hours' time to prepare for a flood, which is not enough to warn people or make adequate preparations. We have demanded data of the Ganges flow in the areas near the Himalayas, but they could not give us the data."

Floods in Bangladesh, where rivers constitute 13 percent of the territory, are perennial woes for the impoverished country of 140 million people.

Bangladesh was hit by a flood in July and August in 2004 that left more than 700 people dead and 38 percent of the country under water, forcing millions to flee their homes.

The World Bank said the flood caused 2.2 billion dollars of damage, or four percent of gross domestic product.