Last year, on December 15, Ukraine ended one of the darkest chapters of the Soviet legacy and opened a new stage in Ukraine’s evolution into a modern European state when it permanently closed the Chornobyl Nuclear Plant.

Closing Chornobyl created the circumstances for a safer and more prosperous Ukraine for future generations. We are reminded of this today on the 15th anniversary of the terrible accident at Chornobyl and are again grateful that an environmental threat has been removed from the Central European landscape.

Today’s anniversary is an occasion for the global community to pause and reflect on the lessons provided by this disaster, to recall the valor and dignity that the people of Ukraine displayed in the face of adversity – and to acknowledge the suffering that many victims of Chornobyl continue to endure throughout the region.

I am proud of the American people’s role in helping to alleviate this suffering – at the time of the tragedy and continuing through today. I am proud of our continued efforts to work with Ukraine to improve nuclear safety and mitigate the harsh social impact of Chornobyl’s closure on the local population.

Much work remains to be done in Ukraine’s transition to a modern European state. This work will require strong and courageous leadership over the coming months and years. It will require real support for democracy and difficult, but necessary reforms. Last year strong Ukrainian leadership and committed international assistance achieved great results in Chornobyl. I urge Ukraine to stay on the path of reform it set out upon last year. Former U.S. President Theodore Roosevelt once noted that “it is only through strife, through hard and dangerous endeavor, that we shall ultimately win the goal of true national greatness.”

I firmly believe that Ukraine’s national greatness rests in Europe, and in its transatlantic and global ties. The United States stands ready to work with Ukraine as it undertakes the political and economic reforms necessary to build these ties that are so vital to the brighter future Ukrainians seek for themselves and their children.