"We are starting the clean-up operations as soon as tomorrow but the ceasefire has nothing to do with it ... The blockade is still on so we cannot go into the sea yet," Environment Minister Yacoub Sarraf told Reuters.

"So, we are going to start operations in Byblos port and we are still waiting for the embargo to be cleared."

Sarraf has called the spill the biggest environmental catastrophe in Lebanon's history and the United Nations Environment Programme (UNEP) has compared it with a 1999 disaster off the coast of France, when the Erika tanker spilled an estimated 13,000 tonnes of oil into the Atlantic Ocean.

Israeli jets hit storage tanks at the Jiyyeh plant south of Beirut on July 13 and 15.

Sarraf said satellite images indicated that it would cost at least US$100 million to clean up, and that the longer the delay, the more areas it would reach and the harder to clean.

"We are working in parallel with Cyprus and UNEP to try to define it," he said. "We are meeting in Athens on Thursday to try to ... get an OK to go in the sea and survey it physically."

Two UN experts arrived in Syria on Aug. 8 to assess the spill that has reached 140 km (87 miles) of Lebanese coastline and the Syrian shore. European Union experts arrived last week.

MARINE LIFE THREATENED

The spill threatens marine species such as Bluefin tuna and sea turtles, ecologists and UNEP say, including the green turtle which is endangered in the Mediterranean.

"This oil slick definitely poses a threat to biodiversity," said Ezio Amato, a biology expert at Italy's ICRAM marine research institute which works with UNEP.

"Because tuna eggs ... float on the water surface, they can be directly affected by this oil slick with potential serious consequences for the tuna population in the Mediterranean."

Black sludge has settled on the rocks, seabed and sand, including Ramlet al-Baida, one of the few white sandy beaches left in Beirut and where local ecologists say turtles nest.

Turtle eggs hatch in July and with the oil in the way, baby turtles will be unable to get to deep water in time.

Green Line, a local conservation group, is beginning its clean-up at a small fishing harbour off Beirut on Wednesday.

It complains the spill has also caused economic damage by robbing fishermen of their livelihoods and discouraging tourism.

"Hydrocarbon has been accumulating in marine life so in some areas the fish will be contaminated. The effects will last for at least six years," said Green Line's Wael Hmaidan.

Kuwait and Norway have sent chemicals and equipment to clean up the oil, mostly heavy fuel which is tough to remove.

"How damaging? I wish it was quantifiable. You have more evaporation of toxic waste, more dispersion of the slick, more poisonous soluble materials going in the sea," he said.