“We have to use this Ukrainian crisis also as something like an education” for the whole of Europe about “how serious the situation can be” for other countries in the region.

A former activist in the Polish Solidarity movement, the trade union that led the fight to topple Communism in the 1980s, Mr. Tusk, 57, ridiculed Russian accusations that the West had created the crisis in Ukraine by orchestrating the protests last year that toppled the pro-Moscow president, Viktor F. Yanukovych. He noted that Moscow had characterized the Solidarity movement as a “one big provocation against Russia” by the West.

“I have no doubts who is the victim and who is the aggressor in this part of the world,” he said. “Personally, I would want maybe more engagement for Ukraine.” He denounced the murder last week of a prominent opposition leader, Boris Y. Nemtsov, in the center of Moscow as a poor omen for freedom and human rights in Russia.

After serving as Poland’s prime minister for seven years, Mr. Tusk stepped down in September to take over as president of the European Council, becoming the first East European to hold one of the bloc’s most senior positions after a laborious period of political horse-trading among member states.

He arrives in Washington at a moment when both Europe and the United States want to present a common front against Mr. Putin and to deepen their cooperation in addressing terrorism. Trans-Atlantic relations are “absolutely the backbone not only of our two continents” but also “the only guarantee that our values like democracy, free markets, free movement and human rights are based on real power,” he said.

Europe’s acute security concerns, he said, made a proposed trade agreement with the United States a strategic priority. He said it was essential that American and European negotiators reach an agreement on the Trans-Atlantic Trade and Investment Partnership a deal strongly opposed by a host of European groups wary of globalization and American-style capitalism.

He acknowledged that the European Union’s complex decision-making made it difficult for the bloc to respond as swiftly and firmly to Russia and other security challenges as Washington would like.