(CNN) For the first time since Russia's invasion of Ukraine, the US is providing Kyiv with the types of high-power capabilities some Biden administration officials viewed as too much of an escalation risk a few short weeks ago.
The $800 million list is driven not only by direct requests from Ukraine, but also in preparation for a new type of fight on the open plains of southeast Ukraine right next to Russia, terrain that plays into Russia's natural military advantages.
The new weapons package represents the starkest sign to date that the war in Ukraine is shifting -- and with it the weapons Ukraine will need if it hopes to continue to stymie a Russian military that has regrouped and resupplied after its initial failures in the opening weeks of the war.
The Biden administration announced the new package included 11 Mi-17 helicopters that had initially been earmarked for Afghanistan, 18 155 mm Howitzer cannons and 300 more Switchblade drones, in addition to radar systems capable of tracking incoming fire and pinpointing its origin.
This package stands out from previous security assistance in part because this tranche includes more sophisticated and heavier-duty weaponry than previous shipments. A US official tells CNN that's by design, arguing that because Russia, which was unable to capture Kyiv, has shifted its strategy to concentrate forces in eastern Ukraine, the US is shifting its own strategy in what it gives Ukraine.
"The contours of what they need is very different," the US official said.
The newly authorized package was announced days after national security adviser Jake Sullivan and Chairman of the Joint Chiefs of Staff Gen. Mark Milley spent more than two hours on the phone with their Ukrainian counterparts reviewing requests. Defense Secretary Lloyd Austin also spoke with Ukrainian Minister of Defense Oleksii Reznikov twice in the last week. Reznikov gave an update of the situation on the ground, which allowed Austin to determine what weapons Ukraine most needed.
Biden delivered the news of the assistance package during a 58-minute phone call with Zelensky from the Oval Office on Wednesday. There was one item Zelensky asked Biden for directly: Mi-17 helicopters. According to a source familiar, the helicopters had initially not been included in the package as of Tuesday night because US officials weren't clear on whether the Ukrainians wanted or needed them at this time. Zelensky made clear to the President on Wednesday that they did.
The weapons being provided are focused on the type of fighting that's likely to take place in the Donbas region -- open terrain rather than the close fighting in urban and wooded areas that's occurred in areas around Kyiv and other Ukrainian cities. The region also borders southwest Russia, allowing Russian forces to avoid the sorts of sustainment, logistics and communication problems that derailed their all-out invasion of the country nearly from the beginning.
Pentagon press secretary John Kirby said Wednesday that the package was tailored to the fight in Donbas, a topography he described as "a little bit like Kansas."
"It's a little bit flatter. It's a little bit more open. And it's the kind of place where we can anticipate that the Russians will want to use tanks and long-range fires, artillery and rocket fire to achieve some of their objectives before committing ground troops," Kirby said.
The new weapons package, Kirby added, was "very much an effort to give the Ukrainians every possible advantage in this fight that's coming."
The Biden administration has faced bipartisan pressure to do more to help Ukraine, particularly in calls to send more powerful weapons. But the administration resisted for weeks, wary of how Russian President Vladimir Putin, with his forces already deployed, would respond. Officials warned the Kremlin may see it as escalatory or an indication that the United States was joining the fight.
The issue was most acutely felt with the MiG-29 fighter jets Ukraine requested. The administration refused to take part in a transfer of the Soviet-era jets from a third country to Ukraine via the United States, rejecting a proposal from Poland.
The US worried, Kirby said on March 9, that "the transfer of combat aircraft right now could be mistaken by Mr. Putin and the Russians as an escalatory step." A large part of the concern internally was over the proposal to fly them into Ukraine from a NATO air base.
Now the rhetoric of the Biden administration appears to have shifted along with the scope of the war. As the US prepares to send in the types of weapons it has not sent since the invasion began, the Pentagon insisted this was part of the US commitment "from the very beginning" to help Ukraine defend itself.
"How that gets interpreted by the Russians -- you can ask Mr. Putin and the Kremlin," Kirby said Wednesday.
For weeks, Zelensky pleaded with world leaders for more arms and equipment. In March, he spoke with the parliaments of 17 countries, as well as three international organizations. He never strayed far from his core message: Ukraine needs more weapons.
He asked Congress for new air defense systems to help defend Ukraine's skies. He requested 1% of NATO's tanks and planes to fight back against Russian forces. And he sought more weapons from Belgium, warning that if Ukraine loses, the European Union loses.
But his calls for heavier firepower went largely unanswered. For the most part, countries sent more small arms ammunition, anti-armor missiles and anti-aircraft missiles, as well as protective and medical equipment.
Now, with Russian forces preparing for a massive assault on the Donbas region, the tide is turning.
"The envelope of what people are prepared to provide has grown considerably in the last couple of weeks," the US official said. Once Ukrainian forces were able to hold off the Russian invasion for the first few days, it put the options for security assistance "very quickly in a different place."
Slovakia provided Ukraine with S-300 anti-aircraft missiles. The Czech Republic sent in T-72 tanks. The United Kingdom announced that it would ship 120 armored vehicles to Ukraine. And now the United States has authorized a range of new and more powerful weapons.
As a sign of the coordination on assistance to Ukraine, the European Union announced it would provide another $544 million in aid on the same day the White House authorized its own $800 million.
The package announced Wednesday marked the first time the US was providing Ukraine with howitzer cannons. Kirby said that several systems would require additional training for the Ukrainians to use them, including the howitzers and counter-artillery radars.
Many of the weapons that are being directed toward Ukraine are heavier, making them more difficult to transport across the country. Ukraine has collected the weapons provided to date from the US and other countries at its western border before moving them to forces around the country.
Kirby said the Pentagon knows "time is not our friend" as Russia prepares its next offensive but that it's working to move equipment into Ukraine's hands as quickly as possible:
"Even before this was announced, we had been moving at very, very fast speed all the other security assistance that we've been providing, frankly at an unprecedented rate."
The Pentagon hosted the CEOs of the military's eight largest prime contractors Wednesday to figure out how to arm Ukraine faster, according to a readout of the classified meeting. The roundtable discussion, led by Deputy Defense Secretary Kathleen Hicks, focused on the Pentagon's objectives to keep supplying Ukraine with arms while being able to maintain the readiness of US forces and support the defense of allies.
This story has been updated with additional developments Wednesday.