The main task of the United Nations Educational, Scientific and Cultural Organisation committee will be to decide whether some 31 sites, including Japan's Mount Fuji and the city of Agadez in Niger, are of "outstanding universal value".
Around 1,300 delegates are due to attend the ten day conference in Cambodia, which is officially opened in the capital Phnom Penh late today with a speech by Cambodian premier Hun Sen. The closing ceremony is to be held in the country's own heritage site, the temple complex of Angkor in Siem Reap.
"About 15 sites are looking likely to be inscribed now, but you know the committee is independent... So the figure is an estimate," said UNESCO spokesman Roni Amelan at a press conference in Phnom Penh today.
He said the number of nominations had been reduced after Vietnam opted to withdraw its bid to list Cat Tien national park after the application was found not to have met World Heritage criteria in an initial evaluation.
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The meeting will also highlight existing sites under threat.
The ancient cities of Aleppo, Damascus and Bosra are among the sites that have been damaged during the fighting and the assessment said "Aleppo in particular has suffered considerable damage".
Amelan said there had been "very deep concern" about the situation in the country, but said it was not clear what action the committee would decide to take.
Australia's Great Barrier Reef is also under consideration for endangered status, with UNESCO noting studies showing "significant loss of coral cover over the past 27 years resulting mainly from storm damage, climate change effects and crown of thorns starfish and concluding that reducing crown of thorn starfish outbreaks are a key factor in restoring the loss".