U.S. military aid packages to Ukraine have shrunk in recent months as the stockpiles of weapons and equipment the Pentagon is prepared to send Kyiv from its own reserves have been reduced, CNN reports.The changes come amid concerns that the readiness of the U.S. military could suffer as U.S. arms manufacturers play catch-up with the huge demand generated by the war against Russia.The shortfall means US President Joe Biden's administration still has $6 billion to arm and equip Ukraine, but the Pentagon is short of the stockpile it is ready to deliver more than two years after the war began, two US officials told CNN.“It's about the stockpiles we have on the shelves, what (the Ukrainians) are asking for, and whether we can meet those requests with what we currently have,” one of the media sources said.According to Pentagon spokesman Maj. Gen. Pat Ryder, the Pentagon has asked Congress for more time to spend the money before it expires at the end of September. That's a stark difference from last winter, when the U.S. administration begged lawmakers for more money to support Ukraine.“Replenishment is also an issue,” the official said. The U.S. is ramping up production of key items such as 155-millimeter ammunition and Patriot missile systems, both to supply Ukraine and to replenish U.S. stockpiles. But this process will stretch over years and will not be able to meet growing demand quickly.