Putin annexed Crimea, a Ukrainian peninsula in the Black Sea, in 2014, after claiming that ethnic Russians in the region were threatened by Ukraine's pro-Western revolution.
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But the festive atmosphere belied the fact that the project has been mired in controversy due to Russia's 2014 annexation of Crimea from Ukraine. The construction of its railway section continues, its opening is scheduled for 2019.
"The United States condemns Russia's construction and partial opening of the Kerch Strait Bridge between Russian Federation and occupied Crimea, which was done without the permission of the government of Ukraine".
The peninsula has until now been hard to access from southern Russian Federation with long queues of vehicles often trying to board ferries, which are not always able to run during winter storms.
Minister for European Affairs Alan Duncan reminded that the Crimea is part of Ukraine, and its annexation is a violation of global law.
Not by saboteurs or protesters or a stage-stealing, fate-sealing politician - but by the orange-and-white cat that roamed the bridge the day before. Ukraine's President Petro Poroshenko slammed Putin's action calling it, "The illegal construction of the Kerch bridge is the latest evidence of the Kremlin's disregard for worldwide law".
The bridge will have a maximum speed of circulation of about 90 kilometers per hour and from tomorrow on it will be officially opened for the circulation of cars and buses.
Meanwhile, Ukraine's security service raided the offices of Russian state media in Kiev and detained one local journalist on suspicions of treason, moves the chief editor of Russia's RT television suggested were linked to the bridge opening.
The project cost 228 billion rubles ($3.69 billion, €3.1 billion) and is the longest bridge in Europe, taking over the Vasco da Gama Bridge in Lisbon, Portugal.
The Embassy of Russian Federation to the United States has claimed that Moscow does not intend to ask the permission for the construction of the transport infrastructure as RIA News reported. The construction of the bridge connecting Crimea to the Russian mainland kicked off in February 2016.