President Joe Biden secretly gave Ukraine permission to use U.S. weapons to strike inside Russia, two American officials said Thursday. The decision is a U-turn that Kyiv’s allies hope helps turn the tide of the war.

The decision, which applies only to the area around the northeastern city of Kharkiv, aims to ensure that Ukrainian forces can strike the Russian military as it attacks or prepares to attack, said the officials, who spoke on condition of anonymity. Long-range strikes inside Russia would not be allowed, they added.

Politico first reported the decision.

On Wednesday, Secretary of State Antony Blinken appeared to leave room for a shift on the issue.

“We haven’t encouraged or enabled strikes outside of Ukraine. Ukraine, as I’ve said before, has to make its own decisions about the best way to effectively defend itself,” he said during a trip to Europe that will include a NATO meeting Thursday. A “hallmark” of U.S. support for Ukraine, he said, “has been to adapt.”

“As the conditions have changed, as the battlefield has changed, as what Russia does has changed,” he added, “we’ve adapted and adjusted, too, and I’m confident we’ll continue to do that.”

Russia launched a new offensive in the Kharkiv region weeks ago. Meanwhile, Kyiv has warned that it could also be massing troops for another incursion in neighboring Sumy.

Ukrainian President Volodymyr Zelenskyy has issued increasingly dire warnings about his country’s being left handicapped, arguing that the restrictions on its use of Western-supplied weapons have given Moscow an unfair advantage.

German Chancellor Olaf Scholz and French President Emmanuel Macron suggested this week that Ukraine should be allowed to hit military targets inside Russia from which missiles were being fired at Ukrainian territory.

NATO chief Jens Stoltenberg had earlier called for Ukraine to be allowed to use Western-supplied weapons to hit targets inside Russia.

Russian President Vladimir Putin has regularly threatened to retaliate to Western involvement in the conflict with nuclear weapons. That has led to fears that allowing Ukraine to use Western weapons to hit targets in Russia risks a dangerous escalation that could turn the conflict into World War III.

This article was originally published on NBCNews.com