Ukraine has an “urgent need” for air defense equipment at “this critical moment” when Russia is carrying out massive strikes on its energy infrastructure, US President Joe Biden’s national security adviser Jake Sullivan said in Kyiv on Friday, AFP reports.

“We recognize the urgent need for air defense at this critical time, when Russia and Russian forces are attacking the civilian infrastructure of this country with Iranian missiles and drones,” Sullivan said during a press conference at the Ukrainian presidency.

In recent weeks, Russia has stepped up its attacks on Ukraine’s energy infrastructure, causing massive blackouts across the country.

According to the Ukrainian authorities, as of Thursday evening, 4.5 million Ukrainians remained without electricity. As of Friday morning, 450,000 people were left without electricity in Kyiv alone, according to the city’s mayor’s office.

Joe Biden’s close adviser Sullivan unexpectedly visited Kyiv on Friday. In the Ukrainian capital, where he met with President Volodymyr Zelenskyi and Defense Minister Oleksiy Reznikov to express, according to the White House, Washington’s “unwavering support” for the Russian invasion.

“The most important thing I came to say today (…) is that the United States will support Ukraine as long as it is needed in this struggle. There will be no wavering, no decline, no weakening of our support,” Sullivan assured the press in Kyiv.