U.S. President Joe Biden announced an additional $800 million in military assistance to Ukraine on Wednesday, expanding the scope of the systems provided to include heavy artillery ahead of a wider Russian assault expected in eastern Ukraine.

The package, which brings the total military aid since Russian forces invaded in February to more than $2.5 billion, includes artillery systems, artillery rounds, armored personnel carriers and unmanned coastal defense boats, Biden said in a statement after a phone call with Ukrainian President Volodymyr Zelenskiy.

Biden said he had also approved the transfer of additional helicopters, saying equipment provided to Ukraine “has been critical” as it confronts the invasion.

“We cannot rest now. As I assured President Zelenskyy, the American people will continue to stand with the brave Ukrainian people in their fight for freedom,” Biden said in a written statement.

The new package includes 11 Mi-17 helicopters that had been earmarked for Afghanistan before the U.S.-backed government collapsed last year. It also includes 18 155mm howitzers, along with 40,000 artillery rounds, counter-artillery radars, 200 armored personnel carriers and 300 additional “Switchblade” drones.

This was the first time howitzers have been provided to Ukraine by the United States.

Pentagon spokesman John Kirby said some of the systems, like the howitzers and radars, will require additional training for Ukrainian forces not accustomed to using American military equipment.

“We’re aware of the clock and we know time is not our friend,” Kirby said when asked about the speed of deliveries.