The Trump administration is locked in a diplomatic push to convince European allies to ban a major Iranian state-controlled airline known to be engaged in illicit transport and espionage operations, according to U.S. officials who spoke to the Washington Free Beacon.

Germany's decision to ban Iran's Mahan Air—a state-controlled entity known to carry out clandestine military operations on the Islamic Republic's behalf—is being viewed as a diplomatic coup by the top U.S. official in Berlin and is said to be generating support for expanding this ban across the European Union, a move that would deal a severe blow to Tehran's international reach, according to U.S. officials familiar with the matter.

The ban on Mahan has been in the works for months, according to senior U.S. officials, who told the Free Beacon the airline is complicit in the Iranian regime's spying and military operations. Efforts to crackdown on Mahan follow a similar pressure campaign by the Trump administration to prevent Iran from airlifting out of Germany millions of dollars.

U.S. officials familiar with the ongoing diplomatic matter described Iran as trying to airlift several planeloads of cash out of Germany, a major cash influx that could have aided Iran's expansionist foreign policy goals, including its operations in Syria, Yemen, and other regional hotspots.

The amount was so large that Iran attempted to use multiple planes to airlift the cash, an effort that was recently stopped in no small part by top U.S. officials stationed in Germany, sources said.

The next leg of the administration's diplomatic push will focus on convincing France and other leading European countries to also enact a ban on Mahan as part of a wide-ranging national security readjustment aimed at collapsing Iran's illicit financial and military channels, officials said.

The United States pursued and cracked down on Iran's efforts to fly the cash out of Germany immediately, officials confirmed.

"The Mahan Air flights were part of that effort to crackdown on Iran's malignant activities abroad," one official told the Free Beacon, speaking only on background about the sensitive diplomacy. "Shutting down the cash transfer last summer and shutting down Mahan Air" were two pressing goals for blunting Iran's malign activity.

"Mahan Air was being squeezed from every angle," the official explained, disclosing that this is part of the Trump administration's larger policy of choking off the Iranian regime through packages of sanctions and other measures.

As part of the behind-the-scenes effort to put the squeeze on Iran, U.S. officials and others also took a close look at Assadollah Assadi, an Iranian diplomat extradited from Germany for his alleged role in a recent plot to bomb Iranian opposition leaders.

Multiple U.S. government agencies "were very suspicious" of Assadi's alleged links to a bomb plot on European soil, sources said.

Germany's decision to ban Mahan received public approval from top U.S. officials, including Secretary of State Mike Pompeo and Richard Grenell, the U.S. ambassador to Berlin. The praise is said to be a sign the United States is working behind closed doors to spread the ban on Mahan across Europe.

"We are thankful for German leadership to shut down Mahan Air," Grenell tweeted. "The safety of German and U.S. citizens is the highest priority."

"The U.S. welcomes Germany ‘s decision to deny landing rights to Iran ‘s Mahan Air," Pompeo tweeted earlier this week. "The airline transports weapons and fighters across the Middle East, supporting the Iranian regime's destructive ambitions around the region. We encourage all our allies to follow suit."

Sources familiar with ongoing diplomatic efforts said that pressure is now being applied to France. The national security implications of allowing Iran unfettered air travel are becoming more clear, sources said, pointing to Iran's ongoing shipment of militants into regional hotspots, as well as its reliance on illicit funding networks tied to terrorists.