The estimate could change as more data comes in on fuel oil leaks from two sunken Russian tankers.
"Now we are waiting for better weather conditions to obtain high quality satellite imagery, which is necessary for analysis of the situation and more detailed modelling," she said, adding that the current focus is on documenting the pollution, modeling its spread and assessing its impact on ecosystems.
Appeals have also been made to convene an extraordinary meeting of the Commission for the Protection of the Black Sea against Pollution and to conduct an independent assessment of the state of the waters and the marine ecosystem.
An estimated 4,300 tons of fuel oil and possibly other oil products are leaking from the two sinking tankers, Volgoneft-212 and Volgoneft-239, which were caught in a storm and sank in the waters of the Kerch Strait, which connects the Black Sea and the Sea of Azov.
The tankers' tracking systems were disabled at the time of the accidents.
On the same day, a Russian floating crane ship, designed to lift heavy loads, was reported to be in distress off the coast of the temporarily occupied Yalta.