Within the framework of a shared strategic vision, intergovernmental solidarity and joint energy projects have become critically important. In the aftermath of the Russia-Ukraine conflict, Bulgaria’s role as a natural gas transit country for the European Union has significantly expanded, positioning the country as a key actor in regional energy security. Bulgaria has historically been one of the countries most dependent on Russian fossil gas. At the beginning of 2022, before Russia invaded Ukraine, approximately 90% of Bulgaria’s natural gas consumption was supplied by Russia. Although Bulgaria was among the first countries to experience a supply cut from Gazprom in April 2022, it has effectively leveraged its geopolitical position to shape its current energy strategy.
Due to its limited natural gas production and growing domestic demand, Bulgaria relies heavily on energy imports. However, its energy cooperation with Türkiye and the development of alternative routes have made Bulgaria an indispensable partner in the EU’s strategy to reduce reliance on Russian gas. Notably, the memorandum of understanding signed between the Turkish Petroleum Pipeline Corporation (BOTAŞ) and its Bulgarian counterpart, Bulgargaz, in 2023 marked a significant milestone in enhancing natural gas security across the Balkan region. Valid for 13 years, the agreement permits the annual transfer of up to approximately 1.5 billion cubic meters of gas, significantly contributing to the gas supply security of both Bulgaria and Europe.
Türkiye’s LNG infrastructure, particularly the Saros FSRU along with four other terminals, has played a central role in supporting this process. Türkiye currently sources gas from 15 countries through seven pipelines and LNG terminals. This diversification is also a key step toward Türkiye’s ambition of becoming a regional gas hub. Following Russia’s invasion of Ukraine, the United States imposed tighter sanctions on Gazprom and Gazprombank, intensifying pressure on energy flows from Russia to Europe. In this context, Russian gas transported via TurkStream has drawn increased attention from both the U.S. and certain EU member states. Although TurkStream technically contributes to Europe’s energy supply security, it has also been subject to criticism for increasing political dependence on Russia. Against this backdrop, the Vertical Gas Corridor has emerged not only as a technical alternative but also as a geopolitical one.
Vertical Gas Corridor
The primary aim of the Vertical Gas Corridor is to establish a north-south-oriented gas transmission infrastructure connecting Greece, Bulgaria, Romania, Hungary and Ukraine. This corridor aims to transport natural gas from the Southern Gas Corridor (SGC), including Azerbaijani gas, LNG supplies from countries such as the U.S. and Egypt, and potentially future sources from the Eastern Mediterranean and Eastern Europe. For the European Union, activating this corridor represents a step toward diversification of energy supply sources. For Türkiye, it strengthens its role as a transit country through the Trans-Anatolian Natural Gas Pipeline (TANAP) and the Greece-Bulgaria Interconnector (IGB), reinforcing its claim to become a regional energy hub.
The significance of the Vertical Gas Corridor goes beyond technical aspects. It is shaped by U.S. sanctions, Europe’s energy dependence on Russia and the strategic energy policy objectives of the EU. As political sensitivities surrounding the TurkStream pipeline continue to grow, the importance of multisourced and multidirectional infrastructure becomes even more evident. A fundamental assumption underlying the development of the Vertical Corridor is that all participating countries – including Greece, Türkiye, Bulgaria, North Macedonia, Serbia, Romania and Hungary – will achieve the desired level of gas system interoperability in line with the latest EU policy objectives.
In a broader context, the Vertical Corridor emerges as a comprehensive gas interconnection initiative encompassing the entire Southeast European region. The corridor will facilitate the transportation of regasified LNG from Greek ports such as the Revithoussa terminal to northern countries, including Ukraine, Romania, Hungary, Slovakia and Moldova. With an annual capacity of 7.5 billion cubic meters, Revithoussa has been supplying gas to Bulgaria since 2019 and will serve as a critical node in this transnational energy network.
The Bulgarian government has announced that the entire corridor is expected to become operational by the end of 2026, enabling the transmission of up to 10 billion cubic meters of gas annually. Initially proposed in 2016 and officially announced in 2023, the Vertical Gas Corridor is repurposing the existing Trans-Balkan pipeline, which was originally used to transport Russian gas southward. The redesigned system now allows for the reverse flow of gas from Türkiye, Greece and beyond to northern countries, including Ukraine, in Central and Eastern Europe.
To secure stable supplies, the Bulgarian government is actively negotiating long-term LNG contracts. Discussions are ongoing with Hungary, Moldova and Ukraine to coordinate joint LNG procurement tenders and secure fixed-price supply agreements, which are seen as vital for regional energy stability. The Vertical Gas Corridor is also part of a broader strategy that includes enhancing cross-border gas transmission between Bulgaria and Türkiye. The current capacity between the two countries is 3.5 billion cubic meters per year and with infrastructure upgrades, this is expected to double. While this expanded capacity may also accommodate increased Russian gas flows via TurkStream, both Bulgaria and Türkiye have expressed a clear commitment to diversifying their energy sources.
The development of this corridor is also expected to enable increased gas imports from Azerbaijan and Central Asia, supporting Türkiye’s vision of becoming a continental energy hub. To eliminate existing transmission bottlenecks, Bulgaria has undertaken projects to expand capacity toward Greece and Romania through the construction of two interconnectors, including parallel pipelines along the Kulata-Sidirokastro and Negru Vodă-Kardam routes. Additionally, the 182.6-kilometer (113.46-mile) Greece-Bulgaria Interconnector (IGB), completed in 2022, now serves as a major conduit for Azerbaijani gas flowing through the Southern Gas Corridor. The Trans Adriatic Pipeline (TAP), which currently transports 10 billion cubic meters of Azerbaijani gas annually to Europe, is expected to double its capacity to 20 billion cubic meters by 2027, further reinforcing the supply chain through the Vertical Gas Corridor.
These developments mark a strategic turning point in Europe’s energy landscape, as Southeast Europe emerges as a vital corridor for LNG and non-Russian gas flows. The Vertical Gas Corridor, driven by Türkiye’s hub initiative and supported by infrastructure cooperation among Greece, Bulgaria and Azerbaijan, is shaping a new energy architecture for the continent. In a region once dependent on a single supplier, collaboration based on a shared strategic vision has become the driving force behind energy security, resilience and market diversification.