WASHINGTON—President Donald Trump has signed off on a decision to provide Ukraine with lethal defensive weaponry, including portable antitank armaments, U.S. officials said Friday, in a major shift in the yearslong conflict between Kiev and separatists backed by Russia.

The decision to send Javelin antitank missiles places Washington closer to the conflict in eastern Ukraine. The administration notified Congress of the decision on Friday, U.S. officials said.

Ukraine has long sought Javelins and other equipment from the U.S. to counter Russian-made armored vehicles in rebel-held areas, but the U.S. had steadfastly avoided steps that officials feared would escalate the conflict.

The move to provide lethal weaponry came as fighting intensified recently and after Russia withdrew earlier this week from a cease-fire monitoring group in the region, spurring concerns of an imminent escalation in hostilities.

The State Department wouldn’t confirm the U.S. decision to send the antitank weapons but said in a statement late Friday that the U.S. would provide “enhanced defensive capabilities.”


​“The United States has decided to provide Ukraine enhanced defensive capabilities as part of our effort to help Ukraine build its long-term defense capacity, to defend its sovereignty and territorial integrity, and to deter further aggression,” State Department spokeswoman Heather Nauert said Friday. “U.S. assistance is entirely defensive in nature, and as we have always said, Ukraine is a sovereign country and has a right to defend itself.”

The decision to supply Ukraine with Javelins was confirmed by officials who said Mr. Trump approved a version of a plan put forward earlier this year by the Pentagon and the State Department, under which the U.S. would provide antitank weapons, including Javelin missiles, ​and other weaponry.

Ever since Russia invaded and annexed Ukraine’s Crimea peninsula in 2014 and began supporting Russian-speaking insurgents in the country’s east, Washington has largely limited its support for Kiev’s military to so-called nonlethal aid and training.

The proposal to move toward lethal weaponry has found support in the Trump administration, particularly as officials are concerned about an increase in violence in eastern Ukraine and see the conflict as an impediment to improving relations with Moscow.


The decision marks the second time this week the administration has taken action likely to antagonize the Kremlin. On Monday, Mr. Trump outlined a new national security strategy that singled out Russia for attempting to upset international order and destabilizing global relationships.

Those moves contrast with overtures by Mr. Trump toward Russian counterpart Vladimir Putin. But earlier this month, Secretary of State Rex Tillerson said the conflict in Ukraine represented a barrier to improved relations.

“We’ve made this clear to Russia from the very beginning, that we must address Ukraine,” Mr. Tillerson said at the time. “It stands as the single most difficult obstacle to us re-normalizing the relationship with Russia, which we badly would like to do.”

After the start of conflict in 2014, the White House considered sending lethal defensive weapons, but President Barack Obama decided against doing so, fearing it would provide Mr. Putin a pretext for further involvement.


Lethal arms also have been resisted by officials in Germany and France, concerned that the move would increase tensions and deepen the conflict.

But U.S. officials previously have told The Wall Street Journal that they expect ​some allies—including the U.K., Canada, Poland and Lithuania—to be open to an increase in military support.

Kurt Volker, the U.S. envoy for Ukraine, has told European officials that the Trump administration sees a narrow window for progress in Ukraine before Russia’s presidential elections, due in March 2018, but that a change in the situation can only be brought about by increasing Moscow’s costs for continued intervention in Ukraine. ​

Some European officials have said they are skeptical that lethal weaponry would change the balance of power, concluding Moscow is prepared to ensure that separatists will always have the upper hand.


Russian officials have long denied supporting separatists and have criticized Western efforts to train the Ukrainian military. Russian officials have previously said that any U.S. move to send weapons to Ukraine would further impair peace efforts.

—Gordon Lubold contributed to this article.

Write to Felicia Schwartz at Felicia.Schwartz@wsj.com