The European Union on Thursday slapped travel bans and asset freezes on 12 more people, closing in on President Vladimir Putin's inner circle to punish him in the escalating crisis over the Russian annexation of the Crimea peninsula.

The move brought the number of Russians and Ukrainians facing EU sanctions to 33, and French President Francois Hollande said it included a lot of crossover with the people the United States is targeting with similar measures.

"We added 12 people, in concert with the Americans," Hollande said.

The 28-nation bloc said the names of the sanctioned would be published Friday. "Some of them are really high-ranking," said EU President Herman Van Rompuy.

The EU leaders also tasked its executive Commission to prepare a raft of economic sanctions that could be imposed if one of the biggest political crises in Europe since the Cold War worsens further.

"We cover all economic areas," said Van Rompuy, implying it could include an arms embargo against Russia.

As Europe got tougher, President Barack Obama announced the United States is also levying a new round of sanctions on individuals in Russia. Russia hit back, imposing entry bans on nine U.S. lawmakers and officials in response to Washington's sanctions.

President Dalia Grybauskaite of Lithuania said the EU was closely behind the United States.

"It is already time to target the close circle of Putin," she said.

Beyond punishing Russia, the EU also wanted to show backing for Ukraine, which lost Crimea to Moscow on Tuesday.

British Prime Minster David Cameron said the two-day summit would also focus on strengthening Ukraine's fledgling government, calling on the 28 EU nations' need to bolster the new Ukrainian authorities with political commitments and economic aid.

Ukraine's Prime Minister Arseniy Yatsenyuk will sign a political agreement Friday with EU leaders, underscoring Europe's commitment to the new leadership in Kiev.

Speaking to France-24 television from Brussels, he called the agreement "the first big tremendous step to make Ukraine really a part of big Europe."

"We do understand that this is only the first step," Yatsenyuk said. "But this will pave the way to real reforms ... that my country urgently needs."

Despite the tough talk, there also is concern in Europe about inflicting too much economic damage as the continent crawls out of a crippling financial crisis.

The EU is Moscow's biggest trading partner, and Russia is the EU's third-largest partner, mostly thanks to exports of raw materials such as oil and gas. Because of the multi-billion trade exchanges, any step toward economic sanctions will not be taken lightly.

"The Russian economy is already hurt by what Putin is doing," Swedish Prime Minister Fredrik Reinfeldt said, adding that a spree of retaliatory sanctions would hurt everyone.

"We need to prepare ourselves and that means, of course, hurting ourselves in a way," he said.