A referendum had previously been scheduled in Crimea for March 30, but the question to be put to voters was whether their region should enjoy "state autonomy" within Ukraine.
The city legislature in Sevastopol, the Crimean port that hosts Russia's naval base, voted late Thursday to declare itself part of Russia and join the referendum. The vote was necessary because the city has an autonomous status making it separate from the rest of Crimea.
Crimea's new leader has said pro-Russian forces numbering more than 11,000 now control all access to the peninsula in the Black Sea and have blockaded all military bases that have not yet surrendered.
EU economic sanctions against Russia could prove painful for Europe since Russia could hit back by turning off the taps to natural gas that is an urgent need for many European countries, including regional giant Germany.
The fallout for Europe from any action targeting influential Russian oligarchs or corporations would also be great. Russian investors hold assets worth billions in European banks, particularly in Britain — which is reluctant to undermine its massive financial services industry. Russia, the EU's third biggest trading partner, bought $170 billion in European machinery, cars and other exports in 2012.
The U.S. sanctions were announced as Secretary of State John Kerry headed into a meeting with Russian Foreign Minister Sergey Lavrov in Rome. Kerry stressed a need for a direct Russian-Ukrainian dialogue and the importance of allowing international monitors into Crimea and eastern Ukraine, but diplomatic progress appeared elusive.
In Simferopol, Crimea's capital, about 50 people rallied outside the local parliament Thursday waving Russian and Crimean flags. "Russia, defend us from genocide," one poster read.
"Only Russia can give us a peaceful life," declared 35-year-old Igor Urbansky, one of the rally participants.
"We are tired of revolutions, maidans and conflicts and we want to live peacefully in Russia," he said, evoking the name of the downtown square in Kiev where tens of thousands of protesters contested the rule of Ukrainian President Viktor Yanukovych, who fled to Russia.
Still not all in the city favored the lawmakers' vote to secede from Ukraine.
"This is crazy. Crimea has become Putin's puppet," said Viktor Gordiyenko, 46. "A referendum at gunpoint of Russia weapons is just a decoration for Putin's show. A decision on occupation has already been made."
Svetlana Savchenko, a Crimean lawmaker, said the choice she and her fellow deputies took in favor of joining Russia will force Moscow to make a decision.
"Now the Russian Federation must begin a procedure — will it take us in or not?" she said.
Rustam Temirgaliev, first vice premier of the Crimean government, said preparations were already underway already to bring Crimea into Russia's "ruble zone."
"At the present moment, a large, important group of specialists from Russia is at work, preparing to assure the entry of Crimea into the Russian Federation," Temirgaliev said.
At the Ukrainian naval base in Novo-Ozerne, the inlet leading to the Black Sea was blocked Thursday by a partially submerged Russian naval vessel, preventing two Ukrainian ships from leaving port. Ukrainian sailors said the Russians had blown up the decommissioned vessel overnight.
Baetz reported from Brussels. Associated Press reporters Sergei Chuzavkov in Donetsk, Dalton Bennett in Novo Ozerne, Julie Pace in Washington, Lara Jakes in Rome, Vladimir Isachenkov in Moscow, David Rising in Berlin, George Jahn in Vienna, and Angela Charlton in Brussels contributed to this report.