European Union leaders said Thursday that they are ready to use their combined power over a long confrontation with economically struggling Russia, if the country’s president Vladimir Putin refuses to change his policy on the crisis in Ukraine. The warning from EU leaders comes after Putin criticized Western sanctions on Russia, and accused the U.S. and EU of undermining his country in an annual press conference on Thursday.

During the conference, Putin said that Russia’s economy could be revived within two years as his government and the country’s central bank have taken “adequate” actions to defend the ruble. However, he also acknowledged that the sanctions over Moscow’s role in the eastern Ukrainian conflict accounted for about 25 to 30 percent of Russia’s economic crisis.

“We must go beyond being reactive and defensive. As Europeans we must regain our self-confidence and realize our own strengths,” Donald Tusk, the former Polish premier, who chaired an EU summit in Brussels on Thursday, was quoted by Reuters as saying. “It is obvious we will not find a long-term perspective for Ukraine without an adequate, consistent and united European strategy towards Russia.”

Although some in the EU have argued that the bloc should shift its focus from supporting Ukraine, and try to ease strained relations with Moscow, leaders eventually decided to remain tough toward Russia while also sustaining mutually beneficial commerce.

“Russia is today our strategic problem, not Ukraine,” Tusk said. “The biggest challenge today is the Russian approach, not only to Ukraine but also to the EU.”

EU leaders made no moves to introduce new sanctions against Russia. However, they said that any easing of current sanctions will depend on how the situation improves in Ukraine, Ria Novosti, a Russian news agency, reported.

“The door is always open if Russia changes its behavior,” Reuters quoted British Prime Minister David Cameron as saying. “If it takes Russian troops out of Ukraine, and it obeys all the strictures of the Minsk agreement, these sanctions can go.”

Putin claimed Thursday that Russia’s stance regarding the Ukrainian crisis was right, while the Western powers were wrong in their conclusions over the issue.