FIRST ON FOX: 100 Republican members of Congress sent President Biden a letter on Thursday calling for fentanyl-related drugs to be permanently labeled schedule one substances.

Wisconsin Rep. Bryan Steil, a Republican, led a letter with over half of the House GOP Caucus to Biden, calling on the president to continue his support of cementing fentanyl’s highly illegal status under the Controlled Substances Act.

"Fentanyl kills more people age 18-45 than car accidents, suicide, or COVID-19," Steil told Fox News Digital in an email statement. "We cannot stand by and watch as Americans are being killed by the flood of fentanyl related substances coming into our country."

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"It is past time for President Biden to take seriously the need to secure our border, and make permanent fentanyl related substances Schedule 1 classification." he continued.

Rep. Bryan Steil, R-Wis., on Dec. 2, 2020.  (Greg Nash/Pool via REUTERS)

Fentanyl-related substances are deadly synthetic opioids ravaging American communities, hitting teens and young adults the hardest – the drugs, alongside the base drug they are altered from fentanyl, are the current leading cause of overdose deaths in the U.S.

"Drug overdoses claim more American lives each year than ever before," the lawmakers wrote in the letter exclusively obtained by Fox News Digital. "Fentanyl and fentanyl related substances are fueling the overdose epidemic, killing 64,178 Americans between May 2020 and April 2021 and making up 64 percent of total U.S. overdose deaths."

The lawmakers also noted fentanyl’s and related substances' potency, which blows both heroin and morphine out of the water exponentially, and pointed out "China has been the principal source of the precursor agents from which fentanyl is produced."

They also urged Biden and his administration to "take immediate action to stem the fentanyl scourge coming from China and across our southern border."

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Fentanyl is also one of the most common illegal substances confiscated from illegal immigrants crossing the southern border, with the lawmakers writing that "U.S. Customs and Border Protection (CBP) reported a 1,066% increase in fentanyl seized at eight Southern Texas ports during Fiscal Year 2021."

The Republicans wrote that the "flood of fentanyl related substances pouring across our borders and the looming February 18 expiration deadline on fentanyl related substances’ current Schedule I classification raise grave concerns for our communities" and called on Biden to "continue to support making fentanyl related substances’ Schedule I classification permanent."

"We again urge you to take immediate and decisive action to protect American communities from this deadly drug," they wrote. "We stand ready to assist in this important mission."

Joe Biden

President Biden is being urged to take immediate action to stem "the fentanyl scourge coming from China and across our southern border." (AP Photo/Andrew Harnik)

According to the U.S. Drug Enforcement Administration (DEA) website, "Schedule I drugs, substances, or chemicals are defined as drugs with no currently accepted medical use and a high potential for abuse."

This puts the synthetic opioids at the same level of illegality as heroin, acid, and peyote — but their scheduling comes with a sunset that goes down on Feb. 18.

The House is considering a bill to extend the classification until March 11 of this year, less than a month later.

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The letter’s wide support saw several high-profile signatories, including GOP Doctors Caucus members Reps. Brad Wenstrup of Ohio and Mariannette Miller-Meeks of Iowa.

A White House spokesperson told Fox News Digital that the administration had presented their recommendations for a long-term approach with a consensus among lawmakers to reduce the amount of fentanyl-related substances going into communities and said the administration is looking forward to working with Congress on the issue.

Congress takes the lead on drug scheduling, as it falls under the Controlled Substances Act.