"We are comfortable that our readiness has not been impacted by the series of presidential drawdown authorities that we've executed," a senior US Defense Department official told reporters on Monday.
The official also said that the US has delivered more than 5,000 of the 5,500 Javelin anti-tank weapons systems Washington has committed to Ukraine.
However, despite the Pentagon's assurances, the Biden administration is looking at alternative plans in case there are shortages.
"We're considering a range of options, if they're needed, to increase production capacity and improve production timelines of both... Javelins, as well as Stingers," White House Press Secretary Jen Psaki said later in the day.
On Tuesday, President Joe Biden will visit a Lockheed Martin plant in Alabama that makes Javelins just as lawmakers and former officials are raising concerns about the US military stockpiles running low. Psaki said the plant Biden is visiting currently can produce up to 2,100 Javelins per year.
However, the US has now distributed one-third of its available Javelin missiles, according to Senator Richard Blumenthal, who said it will take a year to ramp up to full production from the current annual purchasing level of 1,000 per year. He estimated that it could take up to 32 months to replenish the stocks. Raytheon, confirming this, said it will probably not be until 2023-2024 before they can fully replenish both Javelin and Stinger supplies.
Psaki pointed out the domestic benefits of the program to arm Ukraine.
"Each Javelin... missile requires more than 200 semiconductors to make. And boosting domestic chip manufacturing isn’t just critical to making more in America or lowering prices, it’s also a vital component of our national security," Psaki said on Monday.
The Biden administration since Russia's military operation began has committed over $3.4 billion in security aid to Ukraine. Biden last week asked Congress for another $33 billion in aid for Kiev, $20 billion of which would be allocated to security assistance.