President Barack Obama today imposed sanctions on seven top Russian government officials and added four others from Ukraine, including the former president, who the U.S. says threaten peace and security.

The seven officials, which include top aides or advisers to Russian President Vladimir Putin, are Vladislav Surkov, Sergey Glazyev, Leonid Slutsky, Andrei Klishas, Valentina Matviyenko, Dmitry Rogozin, and Yelena Mizulina.

“Today’s actions send a strong message to the Russian government that there are consequences for their actions that violate the sovereignty and territorial integrity of Ukraine, including their actions supporting the illegal referendum for Crimean separation,” the White House said in a statement.

Four other people, allies of the Russian government, were the made targets of U.S. Treasury sanctions under a previous Obama executive order. They are Crimea-based separatist leaders Sergey Aksyonov and Vladimir Konstantinov; former Ukrainian presidential chief of staff Viktor Medvedchuk; and former President of Ukraine Viktor Yanukovych.

White House officials told reporters on a conference call today that sanctions on the four Crimean separatists are aimed at the personal wealth of Russia’s supporters. The U.S. isn’t ruling out additional sanctions, officials said. The U.S. has the ability to escalate pressure, said one of the officials, who was not authorized to speak on the record beyond the official notice.

Serving Notice

“Today’s actions also serve as notice to Russia that unless it abides by its international obligations and returns its military forces to their original bases and respects Ukraine’s sovereignty and territorial integrity, the United States is prepared to take additional steps to impose further political and economic costs,” according to the White House statement.

The executive order signed by Obama also creates the ability for U.S. authorities to target any officials in the Russian government, any individual operating within the arms sector in the country and any individual that owns or controls, acts on behalf of or provides material support to Russian officials.

U.S. officials said the goal was to punish individuals aligned with the Crimea annexation strategy, not necessarily the businesses they oversee.

The U.S. action comes as the European Union imposed sanctions on 21 individuals amid the worst diplomatic standoff with Russia since the Cold War. U.S. officials said some of the individuals sanctioned by the U.S. would overlap with those sanctioned by the EU.