An action plan to tackle the massive oil spill off Lebanon's coastline caused by the conflict is due to be discussed in Greece on Thursday.
Officials have warned of an increased risk to public health
Officials from the UN, the EU and the International Maritime Organisation (IMO) are meeting to agree a way to halt the spread in the Mediterranean.
Oil spilled into the sea following Israel's bombing of a power station.
The slick now covers 170km (105 miles) of Lebanon's coastline and is spreading out to sea.
Environmentalists and health officials have warned that the spill poses a direct threat to marine life and could increase the risk of cancer among people living in the affected areas.
It could take up to 10 years for the affected coastline to recover, they say.
The UN Environment Programme (Unep) and the IMO are jointly hosting Thursday's meeting in the Greek port town of Piraeus.
The objective is "to co-ordinate a common strategy to confront the pollution and to devise actions to prevent the possible expansion of the oil spill," they said in a statement.
Once agreed, the plan will be swiftly put into action, Luisa Colasimone of Unep's Mediterranean Action Plan said.
"A team of volunteers led by experts will clean up the coastline bit by bit. We now have the problem of it spreading out to sea, which will require technical expertise," she said.
Opec's humanitarian arm said on Wednesday it was providing $200,000 to help towards the clean-up effort.
Up to 15,000 tonnes of oil spilled into the sea after Israeli planes bombed the Jiyyeh power plant in mid-July.