LONDON — The United States and Britain formally accused Iran on Tuesday of supplying short-range ballistic missiles to Russia to use in the war in Ukraine, and said they will take measures to punish those involved.

U.S. Secretary of State Antony Blinken, speaking alongside British Foreign Secretary David Lammy during a visit to London, said Iran had ignored warnings that the transfer of such weapons would be a profound escalation of the conflict.

“Russia has now received shipments of these ballistic missiles and will likely use them within weeks in Ukraine, against Ukrainians,” Blinken said. “The supply of Iranian missiles enables Russia to use more of its arsenal for targets that are further from the front line.”

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Joint Statement and Sanctions

Shortly after Blinken and Lammy spoke, the U.S., Britain and Germany issued a joint statement calling the missile transfers “a direct threat to European security,” and said they would impose penalties on Iran, including the cancelation of bilateral air services agreements with Iran and sanctions on individuals and entities involved in Iran’s ballistic missile program. “We will also work towards imposing sanctions on Iran Air,” they said.

The U.S. Treasury and the State Department in the past few years have already imposed economic sanctions on people and companies based in Iran, China, Russia, Turkey and other nations who officials allege are connected with the development of Iran’s drone program.

The sanctions on Iranian drone production tied to Russia’s invasion, which reach as far back as November 2022, were issued despite Iranian leaders’ denials that the country had sent drones to Russia for use in the war in Ukraine.

Among other things, sanctions bar people and firms from accessing property or financial assets held in the U.S. and prevent U.S. companies and citizens from doing business with them.

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Joint Visit to Ukraine

The new sanctions announcement came as Blinken and Lammy prepared to make a joint visit Wednesday to Ukraine, where they will meet President Volodymyr Zelenskyy and other senior officials to discuss bolstering the country’s defenses. The Kremlin is trying to repel Ukraine’s surprise offensive that has claimed hundreds of miles of territory in Russia’s Kursk region.

The accusations about Iranian missiles could embolden Zelenskyy to further ramp up pressure on the U.S. and other allies to allow Ukraine to use Western-supplied missiles to strike deep inside Russia and hit sites from which Moscow launches aerial attacks. President Joe Biden has allowed Ukraine to fire U.S.-provided missiles across the border into Russia in self-defense but largely limited the distance over concerns about further escalating the conflict.

That has not stopped Ukraine from using its own weapons to hit targets deeper in Russia, launching on Tuesday one of the biggest drone attacks on Russian soil in the 2 1/2-year war that targeted multiple regions including Moscow.

Diplomatic Efforts and Future Meetings

The rare joint visit to Kyiv was, unusually, announced in advance, in a public signal of U.S-.U.K. support for Ukraine ahead of what’s likely to be a brutal winter of Russian attacks. It will be followed by a meeting at the White House on Friday between Biden and British Prime Minister Keir Starmer, with support for Ukraine’s defense on the agenda.

Asked whether the U.S. would allow weapons it supplied to strike targets in Russia, Blinken said all use of weapons needed to be allied to a strategy.

He said one goal of the joint visit this week “is to hear directly from the Ukrainian leadership, including … President Zelenskyy, about exactly how the Ukrainians see their needs in this moment, toward what objectives, and what we can do to support those needs.”

“All I can tell you is we will be listening intently to our Ukrainian partners, we will both be reporting back to the prime minister, to President Biden in the coming days and I fully anticipate this is something they will take up when they meet on Friday,” he said.

Word of the alleged transfers from Iran began to emerge over the weekend with reports that U.S. intelligence indicated they were underway, according to people familiar with the matter who spoke on condition of anonymity.

Lammy called the missile transfers part of “a troubling pattern that we’re seeing. It is definitely a significant escalation.”

Iran has denied providing Russia with weapons for its war in Ukraine.

“Iran considers the provision of military assistance to the parties engaged in the conflict — which leads to increased human casualties, destruction of infrastructure, and a distancing from ceasefire negotiations — to be inhumane,” according to a recent statement from Iran’s mission to the United Nations.

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The U.S. and its allies have been warning Iran for months not to transfer ballistic missiles to Russia.

CIA Director William Burns, who was in London on Saturday for a joint appearance with his British intelligence counterpart, warned of the growing and “troubling” defense relationship involving Russia, China, Iran and North Korea that he said threatens both Ukraine and Western allies in the Middle East.

The White House has repeatedly declassified and publicized intelligence findings that show North Korea has sent ammunition and missiles to Russia to use against Ukraine, while Iran also supplies Moscow with attack drones and has assisted the Kremlin with building a drone-manufacturing factory.

China has held back from providing Russians with weaponry but has surged sales to Russia of machine tools, microelectronics and other technology that Moscow in turn is using to produce missiles, tanks, aircraft and other weaponry, according to U.S. officials.