European Council President Donald Tusk says the European Union needs a strategy for dealing with Russia that lasts for years, not months.
"The biggest challenge today is the Russian approach, not only to Ukraine but also to the EU," Tusk, a former Polish prime minister, said.
Tusk was speaking at a news conference early on December 19 at the end of a summit of EU leaders in Brussels.
He called for a strategy that is "tough and responsible" for dealing with Russia and its president, Vladimir Putin, and resolving the Ukraine crisis.
Tusk said "Russia is our strategic problem, not Ukraine."
Earlier, EU leaders adopted new sanctions as further punishment for Russia's annexation of Crimea from Ukraine in March.
The new measures ban all investment in Crimea and stop European cruise ships from traveling there.