WASHINGTON (AP) — The White House announced Thursday that it will rush delivery of air defense interceptor missiles to Ukraine by redirecting planned shipments to other allied nations, as Washington scrambles to counter increased Russian attacks on Ukrainian energy infrastructure.

National security spokesman John Kirby said the U.S. had taken the “difficult but necessary decision to reprioritize near-term planned deliveries of foreign military sales to other countries,” though he wouldn't say which nations would be affected or how many.

“Right now, we know that Ukraine urgently needs these additional capabilities,” Kirby said on a call with reporters, adding, “Obviously more is needed, and it’s needed now.”

The announcement comes after President Joe Biden, during last week's Group of Seven meeting in Italy, suggested such action might be necessary, saying, “We’ve let it be known for those countries that are expecting, from us, air defense systems in the future, that they’re going to have to wait."

“Everything we have is going to go to Ukraine until their needs are met,” Biden said. “And then we will make good on the commitments we made to other countries.”

The U.S. was already sending Ukraine a consistent stream of interceptors for its air defense systems, including for the Patriot missile batteries and the National Advanced Surface-to-Air Missile Systems, or NASAMS. But Kirby said that more was urgently needed as Russia's military has accelerated missile and drone attacks against cities and infrastructure centers “trying to destroy Ukraine's energy system ahead of this winter.”

Russia has resumed its aerial pounding of Ukraine’s power grid while Kyiv’s forces are again targeting Russian oil facilities with drone strikes, as each side seeks to hinder the other's ability to continue fighting.

The number of interceptors to be sent isn't clear but Kirby said it could involve “hundreds” of Patriot interceptor missiles.

Kirby said Ukraine will get prioritized shipments as soon as systems roll off assembly lines for the next about 16 months, and those will provide the country with "enough capability” during that period.

After that, he said, “Countries that have been asked to delay will start to get” deliveries of systems they had already ordered.

Kirby said the move means “a range of countries” will face delays in receiving missile systems that are being diverted to Ukraine but that the shift would not affect Taiwan or what it “continues to need and receive for self-defense" in the face of potential threats from China.

Asked to describe how other countries reacted to the shift, Kirby said they were "broadly understanding of it.”

“They know how serious the need is in Ukraine," he said.