The fierce war in Ukraine has the Pentagon reconsidering its arms stockpiles. If another major war were to erupt today, would the United States have enough munition in its stockpiles to hold its ground?

Pentagon planners are being faced with this question as they continue to supply Ukraine amid its war, which could last years, while Washington says it would intervene if a war breaks out in Taiwan.

While Russia is firing around 20,000 rounds per day, ranging from bullets for automatic rifles to truck-sized cruise missiles, Ukraine is firing back around 7,000 rounds per day, including 155 mm howitzer rounds, Stinger anti-aircraft missiles, NASAMS air defense munitions, and thousands of small rounds.

Kiev's firepower is highly dependent on the US government-funded weapons being pushed to the front lines on an almost weekly basis. The Biden administration announced on Wednesday an extra round of aid, which will see 20 million more rounds of small arms ammunition making it to Ukraine.

"We've not been in a position where we've got only a few days of some critical munition left," Michael McCord, the Pentagon comptroller told reporters this month. “But we are now supporting a partner who is.”

Read:US running low on weapons, munition to give Ukraine: CNN

The US war machine's production lines are not scaled to supply major land warfare; some production lines, like the Stinger missiles, were shut down before.

This has been pressuring the US reserves and has forced officials to ask whether US weapons stockpiles were big enough and whether the US would be ready to respond to a major conflict.

"What would happen if something blew up in Indo-Pacom? Not five years from now, not 10 years from now, what if it happened next week?" Bill LaPlante, the Pentagon's top weapons buyer, said this month at a defense acquisitions conference at George Mason University in Virginia.

The Army uses several of the same munitions that have been proven to be most critical in Ukraine; Stinger missiles, 155 mm howitzer rounds, and High Mobility Artillery Rocket Systems (HIMARS). It is now reviewing its stockpile requirements, Doug Bush, the Army's assistant secretary for acquisition, said Monday.

The military aid packages the US sends either pull inventory from stockpiles or fund contracts with industry to step up production. At least $19 billion in military aid has been committed to date, including 924,000 artillery rounds for 155mm howitzers, more than 8,500 Javelin anti-tank systems, 1,600 Stinger anti-aircraft systems, and hundreds of vehicles and drones. It's also provided advanced air defense systems and 38 HIMARS, although the Pentagon does not reveal how many rounds of ammunition it sends with the rocket systems.

Read: Politico: US shipping some unannounced weapons secretly