April 19 (UPI) -- Amid reports of a massive Russian military buildup along the Ukrainian border and within annexed Crimea, the United States on Monday expressed its "deep concern" over the Kremlin's plan to block foreign naval ships and other state vessels from the Black Sea.
Ned Price, the State Department spokesperson, called the move in a statement part of Russia's history of "aggressive actions" targeting Ukrainian ships and "another unprovoked escalation in Moscow's ongoing campaign to undermine and destabilize Ukraine."
"The United States reaffirms its unwavering support for Ukraine's sovereignty and territorial integrity within its internationally recognized borders, extending to its territorial waters," Price said. "The United States does not, and will never, recognize Russia's purported annexation of Crimea."
Russia invaded Ukraine's Crimean Peninsula in February 2014, attracting the condemnation of world leaders with the U.N. Generally Assembly passing resolutions in support of Ukraine's territorial integrity that March and then passing a second resolution in December calling on states to not recognize any change to the peninsula's status.
Concerns of conflict between Russia and Ukraine have grown amid a recent military buildup of the Kremlin's military around Ukraine's borders at levels Price said have not been seen since Russia's invasion.
Josep Borrell, the high representative of the European Union for foreign affairs and security policy, told reporters Monday that Russia has amassed more than 150,000 troops "with all kinds of materials" including fields hospitals at the Ukrainian borders and in annexed Crimea.
"It is the highest military deployment of the Russian army in the Ukrainian borders ever," he said. "It is clear that it is a matter of concern because when you deploy a lot of troops a spark can jump here or there."
Borrell reiterated the EU's support of Ukraine's sovereignty and territorial integrity during a press conference that followed a meeting of EU foreign ministers, including Ukraine's Dmytro Kuleba, who urged the council to prepare new sectoral sanctions against Russia.
"Individual ones are not sufficient anymore," he said.
As of October, the EU has sanctioned 177 people and 48 entities over their alleged roles in the annexation.
John Kirby, the Pentagon press secretary, wouldn't confirm to reporters during a press conference Monday the number of Russian troops the United States has seen involved in buildup but did say there has been a continued "increase in forces" along the border and in occupied Crimea over the past few weeks.
"We don't believe that this buildup is conducive to security and stability along the border with Ukraine, and certainly not in occupied Crimea," he said.
On Saturday, Russia and Ukraine expelled one another's diplomats amid the escalating tensions.