WASHINGTON ― President Joe Biden’s $106 billion defense spending supplemental request to Congress aims in part to bolster munitions production capacity to continue rushing arms to Ukraine and Israel.

The Senate Appropriations Committee questioned Defense Secretary Lloyd Austin at a Tuesday hearing on the status of U.S. stockpiles and the workforce, supply chain and infrastructure constraints of weapons manufacturers racing to replenish them.

The Senate is formulating its supplemental spending bill encompassing both Ukraine and Israel aid, while the House is set to vote on a stand-alone Israel aid bill later this week.

“There are some limitations in terms of how quickly they can do certain things,” said Austin. “There will continue to be workforce challenges. And when you expand capacity, there’s this issue of the time it takes to build the capacity and make sure the lines are running smoothly.”

Austin noted some defense contractors have required workers to take on additional shifts to keep up with production rates.

“What they’ve done in a lot of cases to meet urgent needs is double and triple shifts so that they can in some cases crank out munitions and weapons at a much greater speed,” he said.

Austin’s comments come as Israel rapidly burns through munitions as it continues to bomb the 2.2 million Palestinians in the Gaza Strip, killing more than 8,500 people and wounding more than 21,500, per the Gaza Health Ministry. Shortly before the hearing, Israel bombed the Jabalia refugee camp, which the Health Ministry lambasted as a “horrific massacre” that killed at least 50 people and wounded hundreds.

It is the latest of many civilian targets Israel has bombed in its campaign to destroy Hamas. Israel launched its campaign following Hamas’ massacre of approximately 1,400 Israelis and abduction of 240 hostages, per the Israel Defense Forces.

On top of that, the Biden administration has less than $5.5 billion remaining to continue transferring weapons to Ukraine as the nation’s slow-moving counteroffensive fails to retake significant tracts of territory.

Biden’s requested defense supplemental includes $44.4 billion to continue arming Ukraine and $14.3 billion in military aid for Israel. That request includes more Iron Dome interceptors to stop Hamas rockets and additional munitions for Israel to continue its bombardment of Gaza.

A large portion of the requested funding would go toward backfilling U.S. stockpiles of weapons the Biden administration has so far sent Ukraine and Israel. There’s also $3 billion requested to expand industrial base capacity.

“We simply do not have the workforce, supply chain or infrastructure necessary to meet the coming threats,” Sen. Deb Fischer, R-Neb., said at the hearing. “Building out this capacity is going to take time and resources, but we can start now by making targeted investments in our munitions production base.”

Biden’s supplemental request includes $30 billion to replenish weapons sent to Ukraine as well as funding to backfill stocks given to Israel.

“As a general rule, we’re going to do everything that we can to meet the demands that we see in both Ukraine and Israel,” Austin said.

The U.S. and NATO continue to face a shortage of 155mm ammunition and are providing those shells both to Ukraine and Israel.

“I’m hearing from industry that they are currently lacking the investment to help quickly accelerate rocket motor production for the [Iron Dome] interceptor missiles to meet the increased demand,” Sen. John Boozman, R-Ark., said at the hearing.

Boozman asked Austin if the supplemental bill should include infrastructure investment to help expand rocket motor production for Iron Dome interceptor missiles.

Austin declined to answer at the hearing and noted he would respond to Boozman in writing, citing the fact that he used to work at RTX, formerly Raytheon Technologies, which coproduces the Iron Dome interceptor with Israel’s Rafael Advanced Defense Systems.

The latest Israel-Hamas war is by far the most destructive, with Israel noting approximately a week after it began its campaign against Gaza that it had dropped more than 6,000 bombs in six days — more than the U.S.-led coalition dropped during any month of its counter-Islamic State campaign.

Sen. Chris Van Hollen, D-Md., said at the hearing Israel has stopped disclosing the number of munitions it has used. He stressed the need to distinguish between Hamas and Palestinian civilians and for Israel to comply with the laws of war.

“Some members of Prime Minister [Benjamin] Netanyahu’s coalition have indicated that all Palestinians in Gaza are responsible for the horrors visited upon Israel,” he said. “And Israel has imposed, as you know, a full siege on the people of Gaza, cutting off most water, food, medicine, electricity and fuel shipments.”