Washington D.C., United States—U.S. President Donald Trump has said that the Pentagon is considering the installation of a permanent military mission in Poland.

Previously during a White House meeting, Polish President Andrzej Duda had requested from President Trump the building of a new, permanent U.S. military base on Polish soil. He argued that this would serve as a deterrent and bulwark against Russian aggression. He proposed that is should be baptized “Fort Trump.” The Polish head of state even proposed to donate more than $2 billion for the funding of the project.

Both presidents said that Russia has been acting aggressively in the region. They cited the examples of Georgia (2008), the Baltics, Crimea, and Ukraine.

“We’re looking at it very seriously, I know Poland likes the idea very much, and it’s something that we are considering, yes,” said Trump.

Earlier in the year, the Polish Defense Ministry released a report on the merits of a permanent U.S. military presence. “Russia is seeking to strengthen its political and economic relations with key European countries at the expense of US national interests. An increased permanent presence in Poland will give America the strategic flexibility it needs to confront and deter these threats,” said the report.

Poland, a former Warsaw Pact member, joined NATO alongside Hungary and the Czech Republic in 1999. This happened against fervent Russian opposition, which had been led to believe that NATO wouldn’t extend an invitation to the former Eastern Bloc countries.

This isn’t the first time Poland has requested for the constant presence of U.S. military units. A concession between no-troops and a permanent deployment has been achieved with the rotation of U.S. armored Brigade Combat Teams (BCT) under Operation Atlantic Resolve.

US Defense Secretary Jim Mattis said the Pentagon is considering the proposal.

“It’s not just about a base. It’s about training rangers, it’s about maintenance facilities at the base, all these kinds of things. There’s a host of details we’ve got to study alongside the Poles,” said Secretary Mattis.

In response, the Russian government has raised concerns over the proposal. Moscow argues that a permanent U.S. military mission so close to Russian soil would undermine NATO-Russian relations and Europe’s security. A Kremlin representative said “the gradual expansion of NATO military structures toward our borders” doesn’t foster “security and stability on the continent. On the contrary, these expansionist actions, of course, lead to counteraction from the Russian side in order to balance the parity which is violated every time in this way.”

President Duda also took the opportunity to raise concerns about the expansion of the Nord Stream 2 gas pipeline. He argued that it would make Europe even more energy dependent on Russia, with the concomitant geopolitical dangers. There is an ongoing debate on the continent about the merits of the pipeline. Germany, whose economy would benefit the most, argues in favor but no consensus has been reached.

“We just think it’s very unfortunate for the people of Germany that Germany is paying billions and billions of dollars a year for their energy to Russia,” said President Trump.