Iran has repeatedly denied that it provided drones to Russia, but this claim has been challenged by Western and Ukrainian officials and media reports.

National security adviser Jake Sullivan initially told CNN in July that the U.S. had information that Iran was preparing to provide several hundred drones to Russia, including weapons-capable unmanned aerial vehicles (UAVs).

The Washington Post, citing unnamed U.S. officials, reported in August that Russia had picked up its first shipment of the UAVs and departed Iran with them on August 19.

Earlier this month, the British Ministry of Defence wrote in an intelligence update that Russia had likely been resupplied with Iranian-made drones after exhausting its previous stock of the UAVs.

A release issued by Iran’s Foreign Ministry on Thursday again took aim at the allegations, this time focusing on what it said were Zelensky’s “repeated accusations and rude remarks against the Islamic Republic of Iran at the U.S. Congress.”

On Wednesday, Zelensky made his first trip outside of Ukraine since the start of the war in late February to visit Washington, D.C., while his country seeks more Western aid for the war.

During an address before a joint meeting of Congress, the Ukrainian president spoke about Russia’s frequent waves of missile attacks and said that Iran had become an ally to Russian President Vladimir Putin’s regime in “this genocidal policy.”

“Iranian deadly drones sent to Russia in hundreds—in hundreds became a threat to our critical infrastructure,” Zelensky said. “That is how one terrorist has found the other.”

Later in the address, Zelensky mentioned the possibility that Russia would send Iranian drones to attack on Christmas Eve and force Ukrainian civilians into bomb shelters.

According to the Iranian Foreign Ministry’s release, spokesman Nasser Kanaani said that Iran has repeatedly responded to “baseless accusations regarding drones leveled by Ukrainian officials against the Islamic Republic.”

Kanaani also said that Iran has not provided either side with military equipment for use in the Ukraine war.

“Mr. Zelensky had better know that Iran’s strategic patience over such unfounded accusations is not endless,” Kanaani said.

The release added that Kanaani advised Zelensky to “draw a lesson from the fate of some other political leaders who contented themselves with the U.S. support.”

The U.S. has announced a series of aid packages for Ukraine since the start of the war. The latest was a $1.85 billion military aid package announced Wednesday that included the MIM-104 Patriot missile defense system.

Newsweek reached out to Iran’s Foreign Ministry for clarification on the advice to Zelensky. Ukraine’s Foreign Ministry was also contacted for comment.