The conflict has intensified in recent years as both countries struggle to find new energy supplies and reduce their dependence on Russian gas.
Romania estimates the disputed shelf may contain reserves exceeding 100 billion cubic metres of natural gas and more than 10 million tonnes of crude, which could theoretically make Romania energy-independent until 2030.
Observers expect the ICJ to make a compromise ruling that will split the waters around Serpent Island, also known as Snake Island, between Romania and Ukraine.
"The court will never meet the demands of either party. It will be a compromise ruling," said Volodymyr Vasylenko, Ukraine`s representative to the International Court of Justice.
"But both parties will take advantage of it ... as (it will) create favourable conditions for both parties to invite foreign investors to develop projects in the area.
At stake are oil exploration and drilling rights in a 12,000 sq km (4,600 sq mile) area of Black Sea waters on the continental shelf in the vicinity of the Ukrainian-owned islet, some 40 km (25 miles) offshore.
Several large foreign companies have expressed interest in investing in the area, including Total (TOTF.PA), Royal Dutch Shell (RDSa.L), BP (BP.L) and OMV (OMVV.VI).
Ukraine argues that Serpent Island is an inhabited, economically active island, which might mean, in the court`s eyes, that the continental shelf around it should belong to Ukraine.
It says around 100 people including military personnel, lighthouse keepers and scientists live with their families on the island, which at 0.17 sq km is about the area of 20 soccer pitches, and has a coastline of high cliffs.
Romania says that Ukraine has only developed activity on the islet with the court ruling in mind, and that it is really an uninhabited rock.
It argues that the islet should have no influence on the course of the maritime border, which could mean that the shelf around Serpent Island would be evenly divided.
However, legal experts say a host of previous ICJ rulings in similar maritime border disputes are too inconsistent to offer any real guide to Tuesday`s ruling.
"After the ruling, we will parcel out the zone we get. For every parcel we will organise public tenders, open for both foreign and local investors," said Gicu Borosi, director at Romania`s Mineral Resources Agency.
Спасибо за Вашу активность, Ваш вопрос будет рассмотрен модераторами в ближайшее время