Six ancient Syrian sites as well as Australia's Great Barrier Reef could be listed as endangered by UNESCO, which Sunday begins its annual session to decide which global cultural and natural treasures merit World Heritage status.
The main task of the United Nations Educational, Scientific and Cultural Organisation committee will be to decide whether 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 officially opened in the capital Phnom Penh late Sunday. The closing ceremony is to be held in the country's own heritage site, the temple complex of Angkor in Siem Reap.
Discussion of new names to add to the already 962-strong World Heritage list is due to begin on Thursday.
The meeting will also highlight existing listed sites under threat.
In her opening address to the session on Sunday, UNESCO Director General Irina Bokova, said "solidarity and political will" is needed "to protect cultural heritage under attack", such as in Mali, Syria, Central African Republic and elsewhere.
"We just cannot standby and watch. We cannot stand still," she said.
"Our capacity to act depends on our integrity."
Syria's civil war, which has claimed some 93,000 lives and reduced huge areas to rubble, has posed a grave threat to its World Heritage sites, according to an assessment by UNESCO.
The ancient cities of Aleppo, Damascus and Bosra are among the sites that have been damaged during the fighting.
"Aleppo in particular has suffered considerable damage," the assessment said.
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".
But despite concerns over water quality and development plans in the area, the preliminary report recommended a stay of execution for another year while improvements are made.
The best-known of the potential new additions to the coveted heritage listing include Mount Fuji, Japan's highest peak at 3,776 metres (12,400 feet) and a national emblem, and Mount Etna, on the east coast of Sicily -- the tallest active volcano in Europe.
Others include the Namib desert flanking southern Africa's Atlantic coast, the magnificent villas and gardens of the Medici in Italy's Tuscany region, the wooden Orthodox churches in the Carpathian mountains of Poland and Ukraine, and the Canadian fishing village of Red Bay, where Spanish Basque whalers operated in the 16th century.
Agadez, a cultural reference point for the nomadic Tuaregs of north-western Africa, was founded before the 14th century and is renowned for several magnificent structures including the Grand Mosque, the Sultan's Palace and its camel and silver market.
"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 Sunday.
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.