Russia’s involvement in Ukraine and Syria combined with aggressive moves across Europe prompted the U.S.’s Air Force's Europe commander to call for a permanent F-22 Raptor base in Europe Wednesday, according to Defense News. The U.S. deployed four F-22s, a single seat stealth aircraft, to Europe last month for the first time.

The move comes as the U.S. tries to reassure European allies of its support amid fears about Russian President Vladimir Putin's next move. “The move to begin introducing the F-22 to the European theater, that decision was made a long time ago in our effort to try and send the message, assures our allies,” said Gen. Frank Gorenc. “I don’t know how well it deterred President Putin; however, it’s done a lot to assure our partners.”

Gorenc said the F-22s were deployed last month from an airbase in Germany, moved to Poland and then finally to Estonia. He said 60 American Air Force personnel trained with their European counterparts. The training showed that Europe has the necessary infrastructure to support a future base.

The announcement came at a time of high tensions between the U.S. and Russia over Moscow’s involvement in both Syria and Ukraine. Earlier this week, the Pentagon’s comptroller announced that the budgets of the four branches of the U.S. military would take into account Russia’s actions -- especially its role in cyber attacks. Pentagon officials have called Russia a threat to the U.S., while Russia has said it sees U.S. actions and the expansion of NATO in Europe as threatening.

Russia continues to deny any direct military involvement in Ukraine. The conflict in eastern Ukraine began in 2014 and has resulted in the deaths of nearly 7,000 people and the displacement of over 1,400,000 people. In recent weeks, Russia has sent military advisers and equipment to Syria and claimed that it was no secret that it had supported Syrian President Bashar Assad. The U.S. said Thursday that it would accept an offer from Russia to discuss the country’s intentions in Syria, the Associated Press reported.