The State Department has approved Poland’s planned $15 billion purchase of Patriot missile systems and other related equipment, the Pentagon announced this week.

The intended purchase is the second phase of a two-part program by Poland to build an “integrated air and missile defense battle command system,” the Pentagon’s Defense Security and Cooperation Agency said in a press release. The State Department approved the first phase of the program, a $10.5 billion purchase plan, in November 2017.

“The proposed sale will support the foreign policy goals and national security objectives of the United States by improving the security of a NATO Ally that is a force for political stability and economic progress in Europe,” the DSCA statement read. The sale will do this by improving Poland’s missile-defense capability “while further enhancing interoperability with the United States and other allies.”

In addition to 48 Patriot-missile-launch stations, the order includes 644 Patriot Advanced Capability missiles, 48 Launcher Interface Network Kits, and 12 Lower Tier Air and Missile Defense Sensors with power systems, among other equipment and parts. Raytheon and Lockheed Martin, the principal contractors on the sale, will also provide flight test support, training, and other logistics support. As part of a potential contract, dozens of U.S. government employees and contractors would remain in Poland for an extended period of time to implement the system.

“There will be no adverse impact on U.S. defense readiness as a result of this proposed sale,” the DSCA statement said.

At the time of the 2017 announcement of the project’s first phase, the State Department said in a statement: “A secure Europe capable of deterring air and missile threats and other forms of aggression promotes peace and stability within NATO and on the European continent.”

Poland has played a key role in bolstering NATO’s defenses in response to the Russian invasion of Ukraine, and prime minister Mateusz Morawiecki said earlier this year that his government will increase its defense spending to 4 percent of GDP. Meanwhile, Washington has further integrated Poland into its military footprint in Europe. In March of this year, the U.S. Army announced that it had established a permanent garrison in the country, and Washington has increased U.S. deployments to the country in recent years.

Other sales to Poland recently approved by the U.S. include a $10 billion planned purchase of HIMARS and a $3.75 billion plan to purchase M1A1 battle tanks.