Much is at stake for Ukraine and for Europe. Let us take the opportunity to take a step back to remember how and why.
In 2014 - 25 years after the fall of the Berlin Wall - a European country once again found itself caught in a make-believe zero-sum game, where outdated principles of spheres of influence and territorial claims incited the Kremlin to use military aggression against a neighboring country.
Today, four years later, Russian aggression against Ukraine is still ongoing and includes the conflict in Donbas and the attempted annexation of Crimea, as well as other attempts at destabilisation.
Russia has set aside international law and principles and has caused instability and unpredictability in Europe.
People are suffering, 1.5 million are displaced and many are dying in a military conflict on European soil, in a neighbour country to the EU.
Europe must not allow itself to forget this, or forget what caused it: a people's free choice of a European future in the winter of 2014, a choice which was attempted hindered through violence by Russia and the corrupt elite - embodied by former president Viktor Yanukovych.
Yet the Ukrainian people prevailed and through democratic elections, they chose a leadership committed to reforms and European values.
Ukraine has come a long way since 2014, not least through the will of the Ukrainian people and its active civil society and with the firm backing of the international community.
The government of Ukraine has undertaken remarkable reforms to ensure economic growth, provide effective governance, facilitate human capital development, implement the rule of law and fight corruption.
The government has launched pension, education and healthcare reforms, prepared the ground for transparent privatisation practices and the efficient management of state-owned enterprises.
In addition, the government has started reforms within the banking sector, the energy sector, public procurements, public administration and de-centralisation, just to mention a few.
Through these reform efforts, Ukraine is slowly revealing its potential.
With the EU-Ukraine Association Agreement and the visa free status, Ukraine has moved closer to the EU.
Trade with the EU has expanded tremendously during the last two years, and the potential is even greater.
Ukraine's membership in the Energy Community and its continued work to ensure full integration into the European energy market are important steps as well.
Further, Ukraine remains a strategic key transit country for gas to the EU. No doubt, Ukraine has much to offer its European neighbours.
For the reform process to succeed, the fight against corruption is crucial.
We welcome the recent breakthrough decision of the Ukrainian parliament, the Rada, to establish an independent high anti-corruption court in line with the Venice Commission's recommendations.
This is a major achievement. Ukraine is committed to establishing the new court as soon as possible.
The Danish-led EU anti-corruption programme in Ukraine stands ready to provide support.
We know that any transition from one system and one set of values to another is lengthy and not without risk. The Ukrainian pursuit of European values cannot be taken for granted. Vested economic and political interests are still present in Ukraine and jeopardise further reforms.
Ukrainian elections in 2019 will be critical for reforms to proceed. And on a daily basis we see Russia literally fighting to counter a Western-oriented Ukraine.
In this environment, it demands strong political will to maintain reform momentum. And it demands building public trust in the government's commitment to reforms. Strong international support remains crucial.
We believe that the rise and success of a reformed and prosperous Ukraine is of paramount importance.
Not only to the Ukrainian people, but also to Europe as a whole. We are all dependent on international law and established principles and rules to determine relations between states.
Denmark's small, open and liberal economy will not be able to prosper without it. We all need to react when faced with challenges to this international framework, violations of a state's territorial integrity and obstruction of its free choice of alliance.
For Ukraine, part of the answer is to stand up for European values and pursue a reformed and prosperous society.
It is in Europe's interest to support these efforts. Therefore, Denmark is donating 530m million Danish kroner (€72m) to good governance and human rights and sustainable economic growth in Ukraine over the next five years.
And therefore, Denmark will host the Ukraine Reform Conference on June 27 in Copenhagen.
The Copenhagen Conference constitutes more than a gathering of governments; it is also a driver for change and a process in Ukraine and internationally in support of a reformed Ukraine and a stronger partnership between Ukraine and the international community.
It is our hope, that the rising of a reformed new Ukraine will demonstrate to Russia that 19th century aggression will not be tolerated nor prove itself worthwhile in our 21st century Europe.
Opinion by Prime Minister of Denmark Lars Lokke Rasmussen and Prime Minister of Ukraine Volodymyr Groysman, EUObserver
Photo: Christopher Bobyn