Iran is a partner in Russia’s “genocidal policy” by supplying drones, Ukrainian president Volodymyr Zelenskiy told a joint session of the US Congress on Wednesday.

In a historic visit to Washington and his first trip abroad since Russia’s invasion began in February, Zelenskiy addressed the United States Congress, thanking for American economic and military assistance and saying that his country is fighting not only to defend itself but security in Europe.

The United States is preparing to deliver Patriot air defense systems to Ukraine after repeated Russia missile and drone attacks on energy infrastructure and other civilian targets. Iran has supplied hundreds of kamikaze drones to Russia that have been used in these attacks.

“If your Patriots stop the Russian terror against our cities, it will let Ukrainian patriots work to the full to defend our freedom,” Zelenskiy said. He added that Russia uses missile attacks to destroy Ukrainian cities.

“More than that, Russia found an ally in this — in this genocidal policy: Iran. Iranian deadly drones sent to Russia in hundreds — in hundreds became a threat to our critical infrastructure. That is how one terrorist has found the other,” Zelenskiy said.

Nato members have strongly condemned Iran for delivering the drones and have imposed punitive sanctions against individuals and companies involved in the production and delivery of the weapon.

The issue of Iranian drones and a growing military alliance between Tehran and Moscow have also hurt the prospects for further talks over Iran's nuclear program and the lifting of crippling sanctions on its economy.