An alleged Lebanese scheme to divert water from a river feeding Israel's largest reservoir could provoke a war, Israeli Prime Minister Ariel Sharon has warned.

Israeli army radio quoted the prime minister as saying on Tuesday that the issue constituted a "casus belli", or "grounds for war".

He was addressing senior military and civilian officials after a cabinet meeting.

Lebanon opened a pumping-station on the River Hasbani in the spring of 2001 to irrigate a drought-stricken village but denies that it plans to dam the river.

The river supplies between 20 and 25% of the water flowing into the Sea of Galilee, an official at Israel's Ministry of Agriculture was quoted as saying by the French news agency AFP.

It rises in Lebanon and flows for about 50 kilometres (30 miles) through its territory before joining the River Jordan and emptying into the Sea of Galilee.

Warning

Army radio said Mr Sharon had notified the United States that Israel could mount military operations should Lebanon begin pumping water out of the Hasbani or its tributary, the River Wazzani.

The Israeli Transportation Minister, Ephraim Sneh, said Mr Sharon had called for a "good and enlightened way" to settle the issue but was ready to "act".

The project has drawn criticism from Israel

"If Lebanon put into effect its project to siphon water from the river, it would be serious enough a reason for Israel to act," Mr Sneh told the radio station.

A spokesman for the United Nations peacekeeping force in southern Lebanon has denied Beirut is siphoning water from the Hasbani, saying it is only piping water to a village suffering a shortage.

At a ceremony to mark the start of the new water supply to the village of Wazzani last March, a Lebanese Government official said it was a "first step".

"This is the first step towards liberating our water, a symbol of sovereignty and simple rights," said Qablan Qablan at the opening of the pumping station.

Israel controlled the Hasbani during its occupation of southern Lebanon in 1978-2000.