WASHINGTON (AP) — Ukraine has used U.S weapons to strike inside Russia in recent days, according to a U.S. senator and a Western official familiar with the matter.

The weapons were used under recently approved guidance from President Joe Biden allowing American arms to be used to strike inside Russia for the limited purpose of defending Kharkiv, Ukraine’s second-largest city.

The official was not authorized to comment publicly on the sensitive matter and spoke on condition of anonymity. Republican Sen. Mike Rounds of South Dakota, a member on the Senate Armed Services Committee, confirmed the strikes with U.S. weapons, but did not say how he was briefed.

Biden’s directive allows for U.S.-supplied weapons to be used to strike Russian forces that are attacking or preparing to attack. It does not change U.S. policy that directs Ukraine not to use American-provided ATACMS or long-range missiles and other munitions to strike offensively inside Russia, U.S. officials have said.

Ukrainian officials had stepped up calls on the U.S. to allow Kyiv’s forces to defend themselves against attacks originating from Russian territory. Kharkiv sits just 20 kilometers (12 miles) from the Russian border and has come under intensified Russian attack.

In advancing in the northeast Kharkiv region, Russian forces have exploited a lengthy delay in the replenishment of U.S. military aid. In addition, Western Europe’s inadequate military production has slowed crucial deliveries to the battlefield for Ukraine.

On Tuesday, White House national security spokesman John Kirby told reporters that he could not confirm that Ukraine had used U.S. weapons at targets in Russia.

“We’re just not in a position on a day-to-day basis of knowing exactly what the Ukrainians are firing at what,” Kirby said. “It’s certainly at a tactical level.”

According to a June 3 report from the Institute for the Study of War, Ukrainian forces struck a Russian S-300/400 air defense battery in Belgorod region, likely with the High Mobility Artillery Rocket System, or HIMARS, on June 1 or June 2. The air defense system was located roughly 60 kilometers (about 40 miles) from the current front line in northern Kharkiv region and more than 80 kilometers (50 miles) from the city of Kharkiv, which is within the range of HIMARS, the institute reported.

Confirmation of the strikes comes as Ukraine’s president, Volodymyr Zelensky, visited Qatar, which along with Saudi Arabia and the United Arab Emirates, has been a key mediators in prisoner swaps and other negotiations between Russia and Ukraine since the war began.

Rounds said he agreed with Biden’s decision to allow U.S. weapons to be used for strikes against Russia under limited circumstances.

“I have no problem with Ukraine using the ATACMS and so forth and all the artillery that we got to be able to take them out before they cause more harm in Ukraine,” he said.

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Associated Press writer Tara Copp and Stephen Groves contributed to this report.