The US announced Friday it would provide Ukraine with "enhanced defensive capabilities," a move that could escalate a conflict between government forces and pro-Russian separatists that has claimed more than 10,000 lives since 2014.
It also threatens to undermine President Donald Trump's calls for improved relations with Moscow.
"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," a State Department statement said.
It added: "US 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 United States remains committed to the Minsk agreements as the way forward in eastern Ukraine."
An ABC news report before the announcement said the US planned to supply Ukraine with anti-tank missiles, including possibly the advanced Javelin system, quoting four State Department officials.
"The total defense package of $47 million includes the sale of 210 anti-tank missiles and 35 launchers. Additional supplies will need to be purchased," the report added.
The announcement came a day after EU leaders agreed to extend tough economic sanctions against Moscow over its meddling in Ukraine for six months, and a week after Ottawa authorized the export of automatic weapons to the country.
Earlier this month, US Secretary of State Rex Tillerson warned Russia that the stand-off over Ukraine was the single most important obstacle to warmer ties between the two countries.