Sen. Dianne Feinstein Dianne Emiel FeinsteinMcConnell says Trump nominee to replace Ginsburg will get Senate vote Top Democrats call for DOJ watchdog to probe Barr over possible 2020 election influence Intensifying natural disasters do little to move needle on climate efforts MORE (D-Calif.) wrote in an op-ed published Monday that the United States "must lead an aggressive, international effort to confront and eliminate" the Islamic State in Iraq and Syria (ISIS) that includes sustained airstrikes in Iraq and Syria.

The chairwoman of the Senate Intelligence Committee wrote in USA Today that the threat posed by ISIS to the U.S. "cannot be overstated."

"This is the most vicious, well-funded and militant terrorist organization we have ever seen, and it is very quickly consolidating its power," she wrote.

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Feinstein, who recently faulted President Obama for being "too cautious" in his response to ISIS, added that she looked forward to hearing his plan against the terrorist group when he addresses the nation on Wednesday.

Feinstein wrote that the two recent videos released by ISIS threatening to kill Americans and showing beheaded U.S. journalists showed ISIS's "true colors."

Feinstein also wrote that she recognized the "reluctance of many Americans to engage in another war in the Middle East."

Still, she wrote, "We either confront ISIS now or we'll have to confront it later — when it will be a much stronger enemy.”

She called ISIS "a sophisticated terrorist army," reminiscent of a military dictatorship.

"ISIS controls extensive resources, military vehicles, heavy weapons and border crossings between Iraq and Syria. It has become a de facto terrorist state," she wrote.

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"Experts estimate that ISIS now has cash and assets worth $2 billion. ISIS adds as much as $1 million per day through extortion, crime, ransom and even the sale of oil on the black market from the several oil fields it controls," she added.

In addition, she wrote that ISIS engages in human rights crimes daily and has killed at least 93 children, detained at least 2,250 women and children, and engaged in the ethnic cleansing of thousands.

"I understand that many Americans don't want to become mired in another war. The conflicts in Afghanistan and Iraq have claimed thousands of American lives and cost more than $1 trillion," she wrote.

"But Americans need to understand ISIS' degree of viciousness as well as what will happen in the absence of U.S. leadership and action," she added.

"If the United States fails to unite and lead the world against ISIS' horrific goals, we could suffer the consequences for decades to come," she wrote.