Poland signed an agreement with the United States for the delivery of a $960 million airspace reconnaissance system to monitor its north-eastern borders, Defense Minister Wladyslaw Kosiniak-Kamysz said on Wednesday.

“Poland will be the second country in the world to use this system,” he said. “The agreement defines our security, it is another act of cooperation between Poland and the USA.”

Poland has boosted defense spending this year to about 4 percent of gross domestic product as it seeks to strengthen its armed forces following Russia’s invasion of Ukraine. It aims to invest 10 billion zlotys ($2.6 billion) in protecting the eastern border.

Under the contract, Poland will receive four aerostats, or moored balloons, which will be stationed at posts along the eastern and north-eastern borders of Poland, assisting Poland’s Air Defense System and Coastal Observation System.

The contract also provides for related logistics and program support. The system will be delivered and fully operative by 2027, said Kosiniak-Kamysz.

According to the head of Poland’s Armament Agency, General Artur Kuptel, describing the system in Polish media earlier this month, radars suspended from the tethered balloons will monitor the sky as far as Ukraine, Belarus, and the Russian exclave of Kaliningrad from Polish air space.

They have the ability to detect a wide range of objects, such as missiles, aircraft, drones and surface vessels in a range of over 300 km.

In February the US Department of State approved the possible sale of airspace and surface radar reconnaissance aerostat systems and related elements of logistics and program support.