Russian naval forces off the coast of Odesa have conducted some shelling of the city in recent days but an amphibious landing would be very difficult and a sign of Russian desperation, according to Mr Bronk.
Odesa is strategically important for Russia as it would cut off Ukraine’s access to the Black Sea.
Russian advances in the east
Fighting continues in the Donetsk and Luhansk regions, where Russian-backed separatists held significant territory before the Russian invasion.
In the north east, Russian troops have surrounded the city of Sumy, bombed vital infrastructure and cut off supply routes.
A similar attempt to encircle Kharkiv, Ukraine’s second-largest city, has been less successful with analysts suggesting Russian forces there are in short supply of ammunition.
Artillery attacks on residential areas of Kharkiv are being investigated by United Nations (UN) prosecutors for possible war crimes.