Congress may soon face pressure to fund the growing costs of the U.S. war with Iran, as military spending climbs into the billions of dollars.

The Pentagon has spent billions in the first week of the conflict, much of it from funds not already included in the defense budget.

Retired Col. Mark Cancian, a military analyst at the Center for Strategic and International Studies, estimated the first 100 hours of the war cost roughly $3.7 billion.

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However, costs have declined as the U.S. military has gained control of Iranian airspace, allowing forces to rely more on shorter-range and less expensive weapons.

Cancian now estimates the conflict is costing about $500 million per day.

Were spending far, far less on munitions than we were in the first couple of days, he said.

The White House has not yet formally requested additional funding from Congress. But sources told Scripps News that a request is expected as concerns grow about the supply of the United States most advanced weapons.

President Donald Trump acknowledged those concerns in a post on Truth Social, writing: At the highest end, we have a good supply, but are not where we want to be.

Cancian said some of the weapons being used are extremely expensive. A single Tomahawk cruise missile can cost more than $4 million.

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The financial impact of the conflict extends beyond military spending.

GasBuddy estimates Americans are spending about $187 million more per day on gasoline than they were a week ago.

A separate analysis by investment firm Raymond James found that if oil prices remain at current levels, higher energy costs could erase any tax savings Americans might see this year from President Trumps One Big Beautiful Bill.

The Senate is expected to take up a war powers resolution Wednesday that could limit President Donald Trump's military capabilities as the U.S. and Israel continue strikes on Iran but the measure is expected to fail, with Republicans largely standing by the president's foreign policy decisions.

The Pentagon has briefed members of Congress on the activities but has not sought congressional approval for the operation. Democrats have argued Trump must get congressional approval to go to war.

"The answers are very unsatisfying when there's no set plan. When you can't hear day after day, we're going to do this, this, this and this. And these are the reasons why you end up with an endless war," Senate Democratic Leader Chuck Schumer said.

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The U.S. military says the first few days of Operation Epic Fury has delivered around twice the number of strikes in Iran than the Shock and Awe campaign of 2003, which marked the beginning of the Iraq War. President Trump has suggested the military campaign could last at least a month.

The Pentagon late Tuesday identified four of the American service members killed in Operation Epic Fury, ranging in age from 20 to 42 Army reservists from Nebraska, Iowa, Florida and Minnesota.

The initial wave of airstrikes killed much of Iran's senior leadership, including Supreme Leader Ali Khamenei. With Iran's leadership decimated, attention has turned to who may lead the country next. One possibility is Mojtaba Khamenei, the son of the Ayatollah killed in the airstrike Saturday. If that selection occurs, it would be viewed by many as a victory for hardliners looking to defend the current Iranian regime.

Trump acknowledged uncertainty about Iran's remaining leadership.

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"I guess the worst case would be we do this and then somebody takes over who's as bad as the previous person. Well, most of the people we had in mind are dead. So, you know, we had some in mind from that group that is dead and now we have another group. They may be dead also based on reports. So I guess you have a third wave coming in. Pretty sure we're not going to know anybody," Trump said.

Iran has responded to the strikes with missiles launched toward Israel and U.S. allies in the Middle East.

The Trump administration is turning its attention to the Middle East this week, with another round of high-profile meetings between U.S. and Iranian officials set to take place in Switzerland.

President Donald Trump has warned that if no nuclear deal is reached with Iran, the outcome will be very traumatic for the nation. U.S. Secretary of State Marco Rubio was in Europe over the weekend ahead of the talks and called the ongoing negotiations "complicated."

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"We're dealing with radical Shia clerics," Rubio said. "We're dealing with people who make political decisions, geopolitical decisions on the basis of pure theology. And it's a complicated thing. No one has ever been able to do a successful deal with Iran, but we're going to try."

An official confirmed to Scripps News that U.S Special Envoy to the Middle East Steve Witkoff will participate in the meeting with Iranian officials this week. He will be joined by President Donald Trump's son-in-law Jared Kushner, who serves as Senior Advisor to the President.

The scheduled talks follow President Trumps order last week to send the USS Gerald Ford to the Middle East. The president described deploying the Navy's newest and most advanced aircraft carrier as a precaution in case we don't make a deal.

Last week, Israeli Prime Minister Benjamin Netanyahu met with President Trump at the White House. Over the weekend, he reiterated his demands for any proposed deal with Iran.

"First is that all enriched material has to leave Iran," Netanyahu said.

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President Trump also appears focused on another issue in the region: rebuilding Gaza. On his Truth Social platform, he announced he will again meet this week in Washington with his so-called Board of Peace members to reveal which nations have pledged more than $5 billion toward Gaza reconstruction.

"Very importantly, Hamas must uphold its commitment to Full and Immediate Demilitarization," he said. "The Board of Peace will prove to be the most consequential International Body in History, and it is my honor to serve as its Chairman."