Polish Defence Minister Antoni Macierewicz on Tuesday said he had approached the US defence firm Raytheon about buying the Patriot missile system.
"Today, I signed the decision to address a letter of request to the US government and the firm Raytheon in regard to ordering the Patriot system," Macierewicz told reporters.
"It concerns a total of eight missile batteries," he said.
Macierewicz, who was speaking on the sidelines of an arms fair in the southern city of Kielce, did not mention any price tag for the deal.
But local media had previously valued it at an estimated five billion euros ($5.6 billion euros).
The Patriot is a mobile air defence system designed to intercept tactical ballistic missiles, low-flying cruise missiles and aircraft.
The Eurosam consortium including MBDA France, MBDA Italy and Thales Group of France is the other contender for the deal.
Macierewicz, who inked a letter of intent with Raytheon in July, said Tuesday that Raytheon was offering "extremely advantageous offset conditions".
Raytheon had promised that Polish firms designated by the government would carry out at least 50 percent of the work involved, he said.