A U.S. delegation is scheduled to brief Polish defense officials eager to buy the F-35 Joint Strike Fighter later this month, U.S. Air Force Secretary Heather Wilson said Monday.

The American team is expected to discuss the costs of buying the Lockheed Martin-made jet as well as the warfighting capabilities it would bring to the Polish military.

“They want to deepen their relationship with the United States of America in part by interoperability of advanced equipment,” Wilson said after a Meridian International Center event in Washington. “Those discussions are continuing. We’re providing the information that might be needed for them to make a decision.”

Poland has been looking to replace its Soviet-era MiG-29 Fulcrum and Su-22 Fitter fighters for several years. Its air force has 31 MiG-29s and and 18 Su-22s, according to the International Institute for Strategic Studies’ 2019 Military Balance. In recent weeks, Polish officials said they would buy 32 F-35s.

“The Polish government has decided that they want the F-35 and they’re in discussions with the United States,” Wilson said Monday.

U.S. officials heading to Poland is a sign that the potential deal is going through the standard foreign military sale process.

The F-35’s design and electronic equipment make it difficult to track for advanced surface-to-air missiles — like the long-range S-300 SAMs that Russia deploys in its Kaliningrad exclave north of Poland.

When the U.S. Air Force deployed F-15 fighters from the 104th Fighter Wing to Estonia in 2016, the jets flew close to those Russian surface-to-air missiles.

“When you take off [in Estonia] you were either in or very close to being in a Russian [surface-to-air-missile] system out of Kaliningrad,” Col. Tom Bladen, operations officer with the 104th Fighter Wing, told Defense One in October 2016.

Earlier this year, the U.S. Marine Corps flew its F-35B jump jets in Syria, where Russia has also deployed the S-300.

Last month, the F-35 program director listed Poland as a potential purchaser along with Greece, Singapore, Spain, and Romania. Vice Adm. Mat Winer submitted his written testimony to the House Armed Services tactical air and land forces subcommittee.

Later in April, Poland Defense Minister Mariusz Blaszczak told local media that a F-35 deal was “not far away.”

While the sale has not been approved by the U.S. State Department, Wilson said it came up when she visited Poland in April.

“[T]hey want to be allied with the United States,” the secretary said. “If there’s one thing that’s really clear, is they fear and detest the Russians.”

Wilson touted Warsaw’s defense spending, which has been increasing for nearly three decades. Poland is one of seven NATO members who spends above 2 percent of its annual gross domestic product on defense.

Buying a fifth-generation fighter is expensive and includes an abundance of training, infrastructure, and maintenance costs beyond the aircraft themselves. Right now, an F-35A, the Air Force version of the Joint Strike Fighter, costs just under $90 million each. For comparison purposes, in January 2018, the Pentagon estimated the sale of 34 F-35s to Belgium at $6.53 billion when all associated costs are factored in.

Poland already flies 48 Lockheed-made F-16 fighters.