The Trans-Balkan Gas Pipeline Moves to New Rules: What This Means for Moldova and Ukraine

From 1 October 2026, gas transportation along the Greece–Bulgaria–Romania–Moldova–Ukraine route is expected to become simpler due to the further introduction of European-style capacity allocation and booking rules.

The changes primarily concern harmonised procedures between transmission system operators, the use of standardised capacity products and the gradual removal of regulatory barriers that have so far reduced the commercial attractiveness of the Trans-Balkan route.

The new framework is designed to make cross-border capacity booking more compatible across the region and to facilitate access to the route for traders. This includes annual, quarterly, monthly, daily and intraday products, as well as more coordinated booking procedures at interconnection points.

Historically, the Trans-Balkan pipeline was used to transport Russian gas southward to the Balkans and Turkey. Today, the same infrastructure can operate in reverse, carrying gas from Greece through Bulgaria and Romania to Moldova and Ukraine.

Potential sources include LNG delivered through Greek terminals as well as Azerbaijani gas. For Moldova, this provides an additional supply route alongside the Iași–Ungheni–Chișinău pipeline and could reduce dependence on individual import directions.

However, the new rules alone do not guarantee a sharp increase in gas flows. The key issue remains cost. The Trans-Balkan route crosses several transmission systems, meaning its commercial attractiveness depends on combined tariffs, capacity-booking costs and coordination between national operators.

High transportation costs have previously been one of the main reasons why the routes of the Vertical Gas Corridor remained underused. The actual effect of the new framework will therefore become clear only after the start of the 2026–2027 gas year, based on booked capacity and physical gas flows.

Comment by the Institute of Danube Research

For Moldova and Ukraine, the significance of the changes lies not in the construction of new infrastructure, but in an attempt to turn an existing pipeline system into a genuinely competitive regional corridor.

The physical possibility of transporting gas from Greece through Bulgaria, Romania and Moldova has existed for some time. The main obstacle has been the economics of the route: a complex chain of bookings and cumulative tariffs could make alternative supplies more expensive than other options.

A transition toward more harmonised European rules reduces administrative and commercial barriers. However, the decisive indicator will be the actual cost of delivering one megawatt-hour of gas to Moldova and Ukraine.

For Moldova, the Trans-Balkan route is strategically important because it broadens the geography of potential supply sources. Together with the Iași–Ungheni–Chișinău interconnector, it creates the basis for a model in which Moldova can source gas from different directions depending on price and market conditions.

For Ukraine, the route may become another southern channel for access to the European gas market and LNG supplies. Its importance may also grow as the Black Sea gas market evolves and new Romanian production comes online.

The central question after 1 October is therefore whether regulatory harmonisation and tariff adjustments will be sufficient to transform the Trans-Balkan route from technically available infrastructure into a regularly used commercial gas corridor.