The United States Navy’s plan to outfit approximately 50 military ships with missile-defense capabilities will draw an “adequate response” from Moscow, a Russian Defense Ministry official said Wednesday. The NATO alliance’s plan to develop an “anti-missile shield” has been a source of continued tension with Russia in recent months.

“We expect some 48, 49 U.S. warships to be converted by 2020 as part of Washington’s global missile shield program,” said Col. Oleg Pyshny, the Russian Defense Ministry official, according to Russian agency Sputnik International News. If completed, the U.S. Navy’s expanded missile defense program would constitute a threat to “the maritime component of the Russian strategic nuclear forces, but Russia will take adequate response steps to offset these threats,” Pyshny added.

The United States and other members of NATO have long planned to develop an anti-missile shield in Europe to counteract potential nuclear threats. Officials previously said the threat of an attack by Iran was the impetus behind the shield’s construction, but Russia has condemned the efforts as a Western attempt to threaten Russia.

NATO planned earlier this year to install elements of its missile shield in Romania and Poland as part of a plan to expand its military capabilities in Eastern Europe. Russia condemned that development and further warned last month that the Baltic States of Lithuania, Latvia and Estonia would make themselves “targets” in a future conflict if they agreed to host the missile shield.

“[The Baltic states] better think about other things – the deployment of missile defense system elements that are targeting our strategic nuclear forces, that is where their problem is, as they become our targets,” Yevgeny Lukyanov, deputy secretary to the Russian Security Council, told the Russian news service  Tass.  

In April, NATO denied Russian accusations that it had moved nuclear weapons into Eastern Europe, stating that any upgrade to the alliance’s military strength in the region was a response to Russian aggression. Western officials have criticized Russia in recent months for its March 2014 annexation of Crimea and apparent involvement in the eastern Ukraine conflict.

“In response to Russia’s actions, we have increased our military presence in the eastern part of the alliance,” NATO said in a statement, according to the Wall Street Journal. “This presence is rotational, defensive, proportional and in line with our international commitments.”