The U.S. can no longer take a reactive stance toward Iran after a new Pentagon report revised the total number of troops killed by Iran-backed groups continues to rise, experts told Fox News Digital. 

"Iran’s regional strategy of working through proxies and carve outs is continuing unabated," Behnam Ben Taleblu, a senior fellow and Iran expert at the Foundation for Defense of Democracies, said. "The open question is, when will the Biden administration ditch tit-for-tat strikes and work to rollback Iran’s Shiite militia network in the heartland of the Middle East?"

President Biden ordered a series of retaliatory precision airstrikes in Syria on Thursday, reportedly killing eight Iranians, after Iran’s Islamic Revolutionary Guards Corps crashed a UAV into a building, killing a U.S. contractor and wounding six other Americans. 

U.S. intelligence assessed the UAV that crashed into a coalition base, which killed the contractor, was of Iranian origin — so President Biden authorized the military to retaliate, the Pentagon said. The Pentagon said the U.S. took "proportionate and deliberate action" that limited the risk of escalation in its targeted response.

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Taleblu said that such a reactionary response will only lead to further attacks and more deaths.

Joint Chiefs Chair Army General Mark Milley visits US base in Syria

U.S. Joint Chiefs Chair Army General Mark Milley, left, speaks with U.S. forces in Syria during an unannounced visit, at a U.S. military base in Northeast Syria, March 4, 2023. (REUTERS/Phil Stewart/File Photo)

"Washington can expect more, not less, drone and rocket attacks on U.S. positions," he continued. "Washington needs a better response ratio to Iran-backed attacks, be they in Syria or Iraq or emanating from one domain but striking the other."

"Pulling punches in Iraq and doubling down in Syria is unlikely to change Iran’s regional calculus."

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A 2019 report from the Pentagon put the total number of Americans killed in Iraq by Iran-backed groups at around 608 – a 20% increase from previously reported numbers. 

Rep. Andy Barr, R-KY, of the House Foreign Affairs Committee, told Fox News host John Roberts on "America's Newsroom" Friday that the Biden administration has shown that "weakness invites aggression."

"When you are engaged in an effort to provide sanctions relief to the Mullahs in Tehran, this invites aggression," Barr argued. "The sanctions relief that the Biden administration is proposing to deliver to Tehran would actually embolden these proxy terror groups and it would help Iran finance the very terrorists who attacked our assets and American soldiers just last night."

Military troops

Troops from the Syrian Democratic Forces Special Operations and the U.S.-led anti-jihadist coalition, take part in heavy-weaponry military exercises in the countryside of Deir Ezzor in northeastern Syria, on March 25, 2022. (Photo by DELIL SOULEIMAN/AFP via Getty Images)

Taleblu concurred with that view, saying that U.S. policymakers at the least must make sure deployed troops have adequate air defense cover to deny and defeat the persistent rocket and drone threat.

Joel Rubin, a former deputy assistant secretary of state under President Barack Obama, told Fox News Digital that Iran's aggressive behavior only increased after Trump withdrew from the nuclear deal, and argued that Trump's sanctions - which remain in place - have not proven effective deterrence to that same behavior. 

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"In fact, we now see that Iran both has the most sophisticated missile program in the Middle East and that it is getting closer and closer to a nuclear weapons capacity, specifically because there are no diplomatic constraints around its behavior," Rubin argued. "It’s past time for Members of Congress to recognize that it’s the lack of diplomatic progress - not the lack of sanctions - that is leaving us vulnerable and insecure."

"Until that changes, we will only continue to see escalating threats and increasing prospects for what would be a devastating war," he added. 

Khamenei and Radan

In this undated photo released on Saturday, Jan. 7, 2023, by the official website of the office of the Iranian supreme leader, Supreme Leader Ayatollah Ali Khamenei, right, speaks with Gen. Ahmad Reza Radan, Iran. (Office of the Iranian Supreme Leader via AP)

Bill Roggio, managing editor of the Long War Journal, told Fox News Digital that the situation in Syria in particular is difficult since the days of a more heavy-handed presence in the region "are long gone."

"As critical as we could be with [the occupation of] Iraq, there are at least Iraqi military units and Iraqi political groups that we could work with," Roggio said. "In Syria, there’s not a lot of good allies."

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To create a more decisive military outcome in the country would require "tens of thousands, if not hundreds of thousands of troops" and a "long-term occupation," which America has no interest in after the results in Iraq and, more particularly, Afghanistan, according to Roggio. 

"We want to keep the troop numbers real low in Syria and Iraq, and in order to do that, you have to make compromises, and then in order to make compromises, you compromise the security of the troops you do have there and you put them at risk," he added. 

Iranian revolutionary guard members marching

Members of the Iranian revolutionary guard march during a parade to commemorate the anniversary of the Iran-Iraq war. (Reuters)

Lisa Daftari, a Middle East expert and the editor-in-chief of The Foreign Desk, said that Iran’s attacks via proxy groups on U.S. targets serve as both a message to the White House and a "flexing tool" to convey to the Iranian people that Western sanctions and efforts to isolate Tehran "will not work." 

"Iran-backed militias have made 29 attacks against U.S. targets in Syria and Iraq just since October without any show of force by American forces," Daftari explained. 

"The fact that there has not been any retaliation or consequences to these targeted hits on American assets tells the mullahs that the U.S. lacks resolve or strength and would rather tread more gingerly through various routes of diplomacy," she continued. "While the White House can make the argument that they’re not looking to escalate, more damage is being done through its passive response."

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"The mullahs will find and declare strength where they can, and right now, the U.S. is enabling them."

The Pentagon and National Security Council did not respond to Fox News Digital requests for comment by time of publication. 

Fox News' Liz Friden contributed to this report.