U.S. President Joe Biden has thanked Slovakia for donating its Soviet-era S-300 air-defence system to Ukraine and said it will be replaced with a U.S.-made Patriot system.

Biden said Ukrainian President Volodymyr Zelenskyy has raised the need to transfer such systems to Ukraine.

“To enable this transfer and ensure the continued security of Slovakia, the United States will reposition a U.S. Patriot missile system to Slovakia,” he said in a statement on April 8.

Biden said that while the Russian military “may have failed in its objective of capturing Kyiv,” it continues to inflict “horrific acts of brutality on the Ukrainian people.”

Prime Minister Eduard Heger said earlier that Slovakia would donate its Soviet-era S-300 air-defence system to Ukraine. Heger announced the donation as he visited Kyiv with top EU officials ahead of a meeting with Zelenskyy.

Zelenskyy mentioned S-300s by name when he spoke to U.S. lawmakers by video last month, appealing for defence systems that would allow Ukraine to “close the skies” to Russian warplanes and missiles.

NATO members Bulgaria, Slovakia, and Greece have the S-300s, which can fire missiles hundreds of kilometres and knock out cruise missiles as well as warplanes.

NATO allies Germany and Netherlands last month sent three batteries of the Patriot air-defence system to Slovakia, which Bratislava said would complement rather than replace the S-300. But it said it was willing to give its S-300 to Ukraine on the condition that it has a proper replacement.

The Patriot system and a team of U.S. soldiers will arrive in Slovakia in the coming days, U.S. Defense Secretary Lloyd Austin said. The length of the U.S. soldiers’ deployment has not been set, Austin said in a statement.

“I salute the generosity of the Slovak government in providing an S-300 air-defence system — a critical defensive capability — to Ukraine,” Austin said in the statement. “It’s a strong testament to how determined Ukraine’s neighbours are to help the Ukrainians defend themselves against Russia’s unprovoked invasion of their homeland.”

He said the move “aligns perfectly” with previous efforts to bolster NATO’s defensive capabilities.

With reporting by AP, AFP, and Reuters