Ukraine and the U.S. are finalizing a deal for Kyiv to secure 25 Patriot air defense systems, Ukrainian President Volodymyr Zelensky said on Sunday, a push that would boost the Ukrainian military’s ability to defend against Russian aerial attacks.

“The difficulty lies in the production queue — a line of countries that have signed relevant contracts. We will be receiving these 25 systems over the years, with different quantities each year,” Zelensky said during a meeting with reporters in Kyiv, according to multiple news outlets.

The Patriot system, which includes launchers, missiles and radar, can cost around $1 billion, and is one of the rare weapons that can intercept Moscow’s ballistic missiles, a necessary component as Russia continues to hammer Ukraine with aerial attacks.

Ukraine will not receive the systems all at once, as it will have to wait for other nations to get the defense system that is in high demand. 

Zelensky said on Monday that Ukraine is working with the U.S. to “ensure that Ukraine still can receive the necessary number of Patriot systems. This is not an easy task, but it is one of the security guarantees for Ukraine — and it will work in the long term.”

The long-term arrangement comes days after Zelensky’s trip to Washington, where he met with President Trump. During their meeting, which was reportedly tense at times, the two leaders discussed ways to end the Russia-Ukraine war. While in the U.S., Zelensky met with top U.S. defense contractors, including Raytheon, which produces the Patriot systems.

“In Washington, I spoke with defense companies that produce Patriots and other weapons we need. The willingness to work with Ukraine is fully sufficient — Ukraine is trusted,” Zelensky said on Monday. “It is important that there be enough support for this at the political level in Washington.”

Earlier this year, Germany sent over two Patriot air defense systems under the Prioritized Ukraine Requirements List, a deal that was forged by the U.S. government with NATO. In total, Ukraine has received at least seven Patriot systems since the war in Eastern Europe began.