Russia and Iran signed a mutual defense and security cooperation pact on Jan. 17 — just days before President Trump’s inauguration. Both nations are primary opponents of the U.S., demonstrated by Russia’s war against Ukraine and Iran’s attempts to assassinate Trump, its regular proclamations of “Death to America, death to Israel!” and its backing of terrorist proxies Hamas, Palestinian Islamic Jihad, the Houthis and Hezbollah. This new pact represents the next move in a long game to shift the global balance of power away from the U.S. and its allies. Although the new administration is coming into office with many pressing agenda items, the Moscow-Tehran partnership needs quick attention before it leads to threats, bloodshed and more war. Trump should reinstate all sanctions that were lifted by the Biden administration and urgently direct the intelligence community to track, analyze and disrupt the Iran-Russian partnership. He should further move to defang Iran’s growing nuclear capacity, neutralize its ballistic missile arsenal and destroy its terrorist proxies. After the collapse of the Soviet Union, Russia and Iran found common ground in viewing the U.S. as a mutual adversary. In 1997, then-Foreign Ministers Evgeny Primakov and Ali Velayati called for the expulsion of the U.S. from the Persian Gulf region. This rapprochement saw Russia supply two reactors to the Bushehr nuclear power station. When Vladimir Putin succeeded Boris Yeltsin, his commitment to revitalizing relations with Tehran was unmistakable. In 2001, Moscow and Tehran signed their first comprehensive cooperation treaty. Putin quickly lifted restrictions on providing biotechnologies to the Iranian military, expanded the transfer of Russian missile technology and coordinated support for Bashar al-Assad in Syria with the ayatollahs and the Islamic Revolutionary Guard Corps. Russia also delivered S-300 anti-aircraft and missile defense systems to Tehran.Russia’s support of Iranian membership in the Shanghai Cooperation Organization and BRICS further solidified Iran’s position as a junior partner, alongside North Korea, in the anti-Western axis formed by China, Russia, Iran and North Korea.The newly signed Russo-Iranian treaty builds on an extensive arrangement in which Iran has been supplying thousands of Shahed drones and short-range ballistic missiles to the Russian military, actively contributing to Russia’s war effort in Ukraine. The pact also proclaims close cooperation in evading sanctions, allowing Moscow and Tehran to leverage their proxies and agents to purchase vital military technology, avoid banking bans and trade oil and commodities on the global black market for much-needed cash.Additionally, Russia and Iran plan to build a massive natural gas pipeline through Azerbaijan. Putin has expressed a desire to accelerate the construction of more Russian nuclear reactors in Iran, while Tehran aims to acquire Su-35 fighter jets, S-400 anti-air missiles and other advanced military equipment from Moscow. Russia has trained and educated thousands of the Iranian nuclear physicists and engineers integral to Iran’s military nuclear program.Despite these developments, Iran finds itself in a precarious economic and defense situation. Years of sanctions, mismanagement and the economic fallout from the pandemic have severely affected its economy, leading to rising inflation and public unrest. Most recently, two significant blows were dealt to Iranian proxies, both of which proved costly for the regime. The first came when Israel turned on Hezbollah for its bombardment of the country’s north since Oct. 8, 2023, carrying out a set of decapitation strikes followed by a military incursion into Lebanon that put the most feared of Iran’s proxies on the back foot. Next, with Hezbollah weakened and distracted, a Turkish-backed coalition of Islamist rebels was able to break out of territory their forces had previously been contained in near Idlib, quickly overthrowing the Assad regime, which Hezbollah had been tasked with defending. Assad himself escaped to Moscow. These developments cost Iran billions of dollars, an untold number of experienced officers and fighters killed and a great deal of prestige. Instead of waiting for the Iranian regime to recover, the Trump administration must swiftly address this pressing threat. The administration must collaborate with allies to prevent the rebuilding of the Iranian air defenses that were damaged in recent Israeli attacks. Tehran’s capabilities to export oil and gas must be limited to throttle the regime’s cash flow, which funds its security apparatus and military adventures. Iran may find support not only in its agreement with Russia but also from perceived Israeli concessions to Hamas in the recent ceasefire deal. Nevertheless, Tehran must be compelled to abandon its destabilizing nuclear program, decommission its ballistic missiles arsenal, halt proxy support throughout the Middle East, recognize Israel’s right to exist and renounce its decades-long “Death to America” agenda. Iran, under its anti-Western theocratic dictatorship, has been a thorn in the side of the U.S. for decades, guilty of taking, torturing and murdering American hostages and attacking American allies. Failure to bring Teheran to heel now will only allow it to continue with a China- and Russia-coordinated program of destabilization, terrorism support and undermining the U.S. in the Middle East, Europe and worldwide. Ariel Cohen, Ph.D., is a senior fellow at the Atlantic Council and the founding principal of International Market Analysis, a global risk advisory boutique based in Washington, D.C. He also serves as managing director of the Energy, Growth, and Security Program and is a senior fellow with the International Tax and Investment Center.