Ukrainian President Volodymyr Zelensky said he had a “constructive conversation” with his American counterpart Joe Biden after Russian rocket attacks on several Ukrainian cities.

“The main issue in the conversation was air defense. At the moment, this is the highest priority in our defense cooperation,” the President of Ukraine wrote on Telegram.

US President Joe Biden has previously condemned the Russian missile strikes, stressing that they demonstrate the “absolute brutality” of Kremlin leader Vladimir Putin’s attack on the Ukrainian people.

“The United States strongly condemns today’s Russian missile strikes on Ukrainian territory, including in Kyiv. As a result of these attacks, civilians were killed and injured, and civilian objects were destroyed. Once again, the sheer brutality of Mr. Putin’s illegal war against the people of Ukraine has been demonstrated,” US President Joe Biden said in a statement.

Since the beginning of the Russian invasion on February 24, the United States has provided Ukraine with $16.8 billion in military support, providing equipment worth $16.8 billion, while imposing a series of sanctions against Moscow.