On December 29, reports suggested the US was considering the possibility of sending Bradley Fighting Vehicles to Ukraine, in future military assistance packages.
"I'm not going to get ahead of security assistance decisions that haven't been made yet, or what we're going to provide in future packages," Kirby said during a background conference. "We have said consistently that we're going to work in lockstep with Ukrainians."
"We're talking to them nearly every day about their needs and the capabilities and requirements, and we're doing the best we can to fill them in as near real time as we can," he added.
Kirby also said the US is working with other nations to see what they can do on capabilities the Pentagon cannot provide.
The lightly armored Bradley vehicle is armed with a 25 mm gun and TOW anti-tank missiles.
During Ukrainian President Volodymyr Zelensky's visit to Washington on December 22, the Biden administration announced a new $1.85 billion security assistance package for Ukraine that includes the Patriot system.
In April, Moscow sent a note to NATO member states condemning Western military assistance to Kiev. Russian Foreign Minister Sergey Lavrov warned that any arms shipments on Ukrainian territory would be "legitimate targets" for Russian armed forces.
Kremlin Spokesman Dmitry Peskov has said the West’s arms provisions to Ukraine undermine prospects for a future peace process.