GAZA - One of Tony Blair's flagship projects as international Middle East envoy - and one of his most concrete achievements to date - was emergency work on a sewage plant in northern Gaza to stop it overflowing and endangering the lives of some 10,000 people.

Now, it has emerged that Israeli forces severely damaged parts of the plant during their 22-day offensive and the project - which was due for completion at the end of this week - has been delayed for two months, with repairs expected to cost US$200 million ($381 million).

Although the damage to Blair's project close to the border with Israel in northern Gaza is modest compared with the overall destruction across the Strip and a Gazan death toll put by the Palestinian Ministry of Health at more than 1200, it has considerable political and diplomatic significance.

It is virtually the only major development aid project which has been allowed to go ahead since Israel imposed its blockade on Gaza 18 months ago.

Blair, who has already raised the issue with Israeli Prime Minister Ehud Olmert and Defence Minister Ehud Barak, had worked intensively to secure Israeli approval for vital components to be brought into Gaza for the works despite Israel's 18-month-long economic siege.

The bulk of the North Gaza emergency sewage treatment project was due for completion in early January and the rest by the end of this week but it is now unlikely to be completed until March at the earliest.

The damage to the project also prolongs the period before pressure can be relieved on the waste water lagoons at Beit Lahiya.

This is necessary to remove the risk of a repeat of the flood which engulfed a nearby Bedouin encampment in March 2007, when five Palestinians were killed in the overflow of raw sewage after the earth walls of the cesspool collapsed and another 1500 local residents were displaced.

A lesser risk is that the level of the sewage lakes will reach the overflow which would pump the sewage on to the crowded streets of Jabalya, another northern Gaza town.

Officials from Blair's office have already begun fresh negotiations with Israeli ministers to bring in replacement components for the repairs, though it was not yet clear who will supply the concrete after the destruction of the Abu Eida works.

Gaza's biggest ready-mix concrete factory, allowed to import cement especially to supply the sewage project, has also been flattened by Israeli bombing.

Blair's office confirmed that the Abu Eida works had been its earmarked concrete supplier.

A preliminary Palestinian Water Authority assessment, seen by the Independent, said the main damage during Israel's military campaign was inflicted on the infiltration basins, including their electrical control room, and the main ductile iron pressure pipe.