President Biden, under pressure from his top national security aides and European allies, allowed Ukraine to carry out limited strikes inside Russia with American-made weapons, opening what could be a new chapter in the war in Ukraine, US officials said Thursday.

Biden’s decision appears to represent the first time that a US president has authorized limited military attacks on artillery, missile bases and command centers within the borders of a nuclear-armed adversary. However, White House officials insisted that the authorization extends only to what they described as self-defense actions, so that Ukraine could protect Kharkiv, its second-largest city, and surrounding areas in the northeast from sustained rocket fire. Bombs and artillery shells from across the border.

“The President recently directed his team to ensure that Ukraine is able to use U.S.-supplied weapons for fire control purposes in the Kharkiv region so that Ukraine can respond to Russian forces that are attacking them or preparing to attack them,” a U.S. official said. This came in a statement issued by the administration. The statement continued: “Our policy regarding prohibiting the use of ATACMS systems or long-range strikes inside Russia has not changed,” referring to the artillery system provided to Ukraine, which has the ability to reach deep into Russian territory.

Inside the White House, Mr. Biden’s deliberations were closely held, known only to a very narrow group of aides. But last week, the New York Times revealed that Secretary of State Antony Blinken returned from a vigil trip to Kiev and privately told the president that his 27-month ban on launching US weapons on Russian soil now puts parts of Ukraine at risk. He said that the Russians are taking advantage of the ban imposed by the president and are launching continuous attacks from a safe haven within the Russian borders.

By then, Jake Sullivan, the president’s national security adviser, had begun to change his view, senior officials said. So did US allies: Britain weeks ago allowed Ukraine to use long-range Storm Shadow missile systems to launch attacks anywhere in Russia, and recently France and Germany took the same position. So did Jens Stoltenberg, NATO Secretary General.

The decision comes after weeks of discussions with the Ukrainians after Russia began a major offensive on Kharkiv.

Because Kharkiv is so close to Russia, Ukrainian President Volodymyr Zelensky has repeatedly pressed Mr. Biden and his aides for the right to respond inside Russia. Mr. Biden has ignored these requests for months, fearing that the use of American weapons would escalate the conflict — and put the United States in direct confrontation with Russia.

When he repented, it was in the narrowest of ways. US officials said Biden’s permission was only for Ukraine to strike military sites in Russia used to attack the Kharkiv region. Russia’s attacks in other areas – even near the capital, Kiev – cannot be responded to using American weapons.

Mr. Biden’s decision was reported earlier Thursday by Politico.

US officials said the Pentagon is tasked with giving Ukraine precise guidelines on what it can strike in Russia. It was actually conveyed by Secretary of Defense Lloyd J. Austin III to General Christopher J. Cavoli, the four-star commander of U.S. European Command and Supreme Allied Commander Europe. The officials said that it was General Cavoli who conveyed the decision to Ukraine.