Some sources also raised concerns about US production of additional weapons systems, including HARMs anti-radiation missiles, GMLRS surface-to-surface missiles and the portable Javelin anti-tank missiles – although the US has moved to ramp up production for those and other systems.While the US will not be able to provide high-end munitions to Ukraine indefinitely, assessing whether the US is “running low” on stockpiles is subjective, one senior defense official said, as it depends on how much risk the Pentagon is willing to take on.A major manufacturing challenge One reason for the concern about low stockpiles is that the US industrial base is having difficulty keeping up with demand quickly enough, the sources said.“We have been able to transfer equipment from US stocks without degrading our own military readiness and continue to work with industry to replenish US inventories and backfill depleted stocks of allies and partners.” At a press conference Wednesday following a meeting of the Ukraine Defense Contact Group, Austin touted the commitments of a half-dozen countries providing additional weapons to Ukraine, including Greece pledging more 155mm ammunition.We will be there for as long as it takes to keep Ukraine free.” The degree to which weapons stockpiles are running low varies system by system, as the US defense industrial base is better equipped to ramp up production of some weapons, while others are more difficult – or the production line has been shut down altogether and can’t be easily resumed."