Russian President Vladimir Putin Friday signed legislation completing the annexation of Crimea, while Ukraine initialed a deal for closer political cooperation with the European Union.
The Kremlin signing ceremony took place after the Federation Council, the upper house of Russia's parliament, voted unanimously to incorporate the Crimea region into Russia. The lower house ratified the treaty on Thursday, just four days after Crimean residents voted in a referendum to break away from Ukraine and join Russia.
President Putin and Crimean leaders signed the treaty on Tuesday, and the Kremlin said the treaty came into force on the date it was signed.
In Brussels, meanwhile, Ukraine's interim Prime Minister Arseniy Yatsenyuk signed a political association agreement with the European Union. Also Friday, the EU added 12 people -- all Russian or Crimean -- to a list of those subject to travel bans and asset freezes, raising the number of such individuals to 33.
Among those newly added to the EU sanctions list are Russian Deputy Prime Minister Dmitry Rogozin and Dmitry Kiselyov, the controversial TV anchor who heads the Russian government's Rossiya Segodnya news agency.
The United States has also imposed sanctions on Russian officials -- including several members of President Putin's inner circle -- and a prominent Russian bank.
President Barack Obama says he is considering more penalties against entire sectors of the Russian economy. He says those plans are being formulated in conjunction with European allies.
In a meeting Friday with his advisory Security Council, Mr Putin said for now, Russia will hold off on imposing sanctions on the United States in retaliation for U.S. sanctions against Russia over the Ukraine crisis.
However, his spokesman, Dmitry Peskov, told reporters separately that Russia will respond in kind to the latest U.S. sanctions, which target Russian officials and members of President Putin's inner circle. "We will respond every time," Peskov said.
And the Russian Foreign Ministry said in a statement Friday that Russia will "respond harshly" to the latest round of U.S. sanctions.
U.N. Secretary-General Ban Ki-moon met Friday with Ukraine's acting president, Oleksandr Turchynov. Following the meeting, Mr. Ban said the crisis could only be resolved "through peaceful diplomatic solutions based on the principle of the United Nations Charter, including respect for the sovereignty, unity and territorial integrity of Ukraine."
On Thursday, the U.N. secretary-general met with President Putin and Russian Foreign Minister Sergei Lavrov in Moscow. Mr. Ban said he urged the Russian leader to prevent "any unintended incident" in or near Ukraine that could aggravate tensions in the volatile region.
Moscow retaliated against the U.S. sanctions with travel bans on nine Americans, including Republican Senator John McCain, Democratic Senate Majority Leader Harry Reid and Republican Speaker of the House of Representatives John Boehner.
In another development, U.S. Defense Secretary Chuck Hagel spoke for nearly an hour with Russian Defense Minister Sergei Shoigu. A Pentagon spokesman says Hagel asked why Russian troops are deploying along Ukraine's eastern southern borders. The spokesman said Hagel was assured that the troops are conducting maneuvers and have no plans to enter Ukraine.
Ukrainian officials say armed pro-Russian forces seized three Ukrainian warships in Crimea's Sevastopol Bay Thursday.
Ukraine authorities said Tuesday that Kyiv has drawn up plans to evacuate Crimea, and will seek U.N. support in turning the peninsula into a demilitarized zone. Ukraine Defense Council Secretary Andriy Parubiy also said Ukraine is planning to hold military maneuvers "with our allies." He did not elaborate.