Ukraine's Deputy Prime Minister and Minister for European Integration Olha Stefanishyna is in Luxembourg on Tuesday to open accession negotiations with the European Union.

For Estonia, the past 20 years in the EU have been a success story – the country's economy and people's incomes have nearly tripled, and Estonia has received the most EU support per capita. Additionally, Estonia ranks very high in various global indices of democracy, human rights and media freedom, thanks in part to reforms made during EU accession.

Encouraged by its success story, Estonia supports further EU enlargement. Pursuing and achieving EU membership boosts Ukraine's economic development and reforms and serves as a significant security guarantee.

However, it is still uncertain when Ukraine might become an EU member. For Estonia, it took nearly ten years from application to accession, with negotiations lasting five years.

Accession negotiations take time and require extensive groundwork, as a country must adopt all EU legislation before joining, and its economy must be strong enough to compete in the EU's internal market.

The EU cannot offer Ukraine fast-tracking or special treatment, but with political will, it is possible for Ukraine to complete accession negotiations within five years, potentially making membership a reality by 2029. Political will is crucial, both from the EU and Ukraine itself, as implementing reforms is often politically challenging, although their long-term impact is in the country's and its citizens' best interest.

If Ukraine joins the EU in 2029 or later, it will be stepping into a different union than the current one. Alongside discussions of new enlargement waves, there is increasing talk about reforming the EU itself. Internal reforms have been publicly called for by both German Chancellor Olaf Scholz and French President Emmanuel Macron.

No one disputes that the union must remain functional if all current candidate countries join. However, there is no political will among member states to amend the foundational treaties in the near future, as the current treaties are considered "enlargement-proof." Opening the treaties would be a very complex, laborious and time-consuming process.

It is clear that the EU's multi-annual budget will also change. The current budget period ends in 2027, and the next one will have to take into account the enlargement of the EU with new member states.

If a country the size of Ukraine joins, it means that the support amounts Estonia receives from the EU will decrease.

This change will not happen overnight, but over time, Estonia will transition from being one of the largest beneficiaries in the EU to becoming more of a contributor to the EU budget. Already, Estonia's GDP per capita is ahead of some earlier joiners (such as Greece) and most of those who joined the EU at the same time as Estonia.

Changes are also needed in the Common Agricultural Policy because Ukraine is a large and efficient agricultural country, and under the current system, other countries would lose nearly 20 percent of their subsidies.

At the same time, enlargement is not the only reason the budget needs reforming.

The EU budget must change regardless to allocate more funds for the green and digital transitions, enhance the union's competitiveness and defense capabilities and solidify its geopolitical role. Enlargement would provide the necessary additional impetus for budget reform.

It is a misconception that Ukraine would only benefit from the EU. As an EU member, Ukraine would have much to offer in return.

For example, Ukraine is extremely rich in natural resources, including abundant rare earth elements and lithium, which are crucial for renewable energy storage. As a major agricultural country, Ukraine's grain exports are vital for global food security. Additionally, the country has enormous potential in the green industry, such as solar energy production.

Post-war economic growth in Ukraine will lead to increased consumption, which would positively impact the EU's internal market. The modernization of Ukraine also presents new opportunities for Estonia's economy and entrepreneurs, such as participating in Ukraine's reconstruction. Already, Estonia has helped build a kindergarten in Ovruch, combining Estonia's top-notch wooden construction and innovative educational experience.

Russia's full-scale aggression in Ukraine and hybrid attacks have irreversibly changed Europe's security situation. Estonia has pushed within the EU for countries to strengthen their defense capabilities, defense industry, military mobility and cybersecurity. Ukraine will have a significant future role in the EU's security and defense policy, as it will become one of Europe's largest and strongest military forces with substantial wartime experience, and its defense industry is already considerable.

Ukraine's path to the EU will not be easy, without obstacles and significant challenges, but it is existentially important for Estonia to support it in every possible way.

Leaving a vacuum or gray zone between Russia and the European Union significantly weakens European security and the economy. A rules-based world order and international law, which President Lennart Meri has called the "nuclear weapon of a small state," are the only ways to protect Europe's and Estonia's security.

Ukraine's accession to the EU is a crucial part of Estonia's security. Estonia has much to gain from Ukraine's EU membership, and we must do everything to make it a reality.

The author is expressing her personal views in the article.