KYIV -- Ukraine has showcased the firepower of the Javelin antitank missile systems given to it by the United States last month in a performance President Petro Poroshenko called "a dream come true."

"Finally, this day has come -- and today, on May 22, for the first time in Ukraine, a test of the third-generation Javelin antitank complex took place," a grinning Poroshenko told his soldiers in a video of the closed test published on his Facebook page. "Thanks to them, the combat capabilities of the Armed Forces of Ukraine have increased significantly."

RFE/RL was first to report the delivery of 37 Javelin launchers, including two spares, and 210 missiles to Kyiv in April.

The U.S. State Department approved the sale of the Javelin systems to Ukraine at an estimated cost of $47 million in March.

Poroshenko on May 22 personally thanked U.S. President Donald Trump, Vice President Mike Pence, Secretary of Defense James Mattis, Secretary of State Mike Pompeo, and the U.S. Congress "for supporting Ukraine and adopting a decision to provide Javelin antitank missile systems."

Kyiv and Washington have said that the Javelins will help Ukraine build its long-term defense capacity and keep Russian aggression at bay.

Russia's Foreign Ministry warned that the weapons may further inflame tensions between Moscow and Washington and push Ukraine "toward reckless new military decisions."

"Of course this is a defensive weapon and will be used only when there is an attack by the Russian Federation on positions of Ukrainian forces,' Poroshenko said at the test.

The special U.S. envoy for Ukraine, Kurt Volker, has said that the Javelins are being stored in a secure facility far from the front line of the conflict in eastern Ukraine's Donetsk and Luhansk regions, where government forces continue to fight Russia-backed separatists.

In its fifth year, the fighting has killed more than 10,300 people.

The Javelin test came amid what international observers of the Organization for Security and Cooperation in Europe's Special Monitoring Mission (OSCE-SMM) in Ukraine said on May 21 has been the deadliest week of the year in the conflict zone, with heavy weapons banned by a tenuous peace accord agreed in February 2015 used against populated areas.

In the test video, Poroshenko appears pleased with the performance of the missile, which is seen hitting a tank in a sprawling field. The president is shown smiling while lauding the "extremely high efficiency" of the weapon.

"You saw the happy faces of soldiers," the president said. "Today, their dream has come true."

"It has a very symbolic meaning," he added, "because it is a symbol of cooperation with our American partners."