(CNN) Top military and Homeland Security officials are considering classifying fentanyl as a weapon of mass destruction, according to an internal DHS memo.

The synthetic opioid, blamed in health surveys for surging drug overdose deaths in the United States, has for decades concerned national security officials because of its potential widespread lethality in terror attacks, and in recent months, officials from DHS and the Pentagon have met to discuss an official WMD designation as a tool to disrupt the drug's widespread availability on the black market, the memo says.

"Fentanyl's high toxicity and increasing availability are attractive to threat actors seeking nonconventional materials for a chemical weapons attack," the DHS assistant secretary for countering weapons of mass destruction, James F. McDonnell, wrote in the memo, which was obtained by the military news publication Task & Purpose

A DHS official confirmed the authenticity of the memo, which was sent to then-DHS Secretary Kirstjen Nielsen in February.

The national security threat posed by fentanyl has remained largely out of the public eye, but the Trump administration has made thwarting its illegal distribution a centerpiece of the campaign against the opioid crisis.

Fentanyl and its derivatives were behind 30,000 of the 72,000 overdose deaths in the US in 2017, according to the National Institute on Drug Abuse.

Versions of the drug, which has legitimate medical use as a painkiller, are widely produced in China and can be purchased on the dark web in the US. Mexican cartels and elements of the heroin trade have been known to use fentanyl as an additive to increase the potency of other illegal drugs.

Late last year, after pressure from the Trump administration, the Chinese government said it would add fentanyl to its list of controlled substances in a significant shift that aims to curb the drug's manufacturing in the country.

Congress has also set new standards on the US Postal Service that will help customs inspectors screen and interdict packages with fentanyl and other opioids at ports of entry.

"Disturbingly easy" to weaponize

Despite these efforts, it would be "disturbingly easy" to use the drug in a chemical attack, said Andy Weber, the former assistant secretary of defense for Nuclear, Chemical and Biological Defense Programs.

"Now that there's actually a market where one can buy large quantities of fentanyl analogues, it eliminates the capability gap and it makes it accessible to terrorist groups," Weber said. "It's a game changer. In my lifetime I've never seen a weapon of mass destruction that is part of an existing black market."

There are other officially-designated WMDs that are made from easily obtainable items, like ricin, which is extracted from the castor bean, though weapons experts said the threat posed by fentanyl and its derivatives are more significant.

"It's as bad as it seems," said a government consultant who requested anonymity to discuss countering-WMD projects he has worked on. "Because of its strength, it's like nothing else that we've seen, beyond radiation, nuclear, chemical and high explosive. It's something that is potentially very, very dangerous."

Fentanyl could be weaponized to devastating effect through its distribution in air and water systems.

US defense officials first noted the danger of a fentanyl attack when the Russian military in 2002 pumped it into the ventilation system of a theater in Moscow that had been taken over by Chechen rebels, according to Weber.

Dozens of hostages were killed by the fentanyl gas, along with the insurgents.

"That's when we at the Pentagon started to realize that militaries were developing fentanyl analogues as a form of chemical weapon and that we needed to start working on countermeasures," Weber said.

Formal designation proposed

According to the memo, there has been "reinvigorated interest" in addressing fentanyl as a WMD "due to the ongoing opioid crisis ," and in recent months, senior DOD leaders, including the commander of the US Southern Command, have proposed the formal designation.

Another former Defense Department official, who requested anonymity to speak to CNN about sensitive topics, said the current consideration of fentanyl as a WMD is part of a broader discussion between national security officials around the classification of pharmaceutical-based agents.

DHS also had "informal discussions on the topic" in the first two months of this year between its sub-agencies and a number of DOD divisions, McDonnell wrote in the memo.

In statements, DHS and US Southern Command both said that they are "constantly assessing" a range of threats in partnership with other agencies, but declined to comment on the specifics of those conversations.

Countering illegal shipments

Designating fentanyl as a WMD would allow national security officials to more effectively divert resources to building technology that could detect shipments of fentanyl.

The Defense Department has been developing capabilities against non-traditional chemical weapons, like fentanyl, according to the memo, but "certain operational [countering weapons of mass destruction] entities at DOD and elsewhere have been slow to act due to concern of getting pulled into the counter-narcotics mission," the memo says.

An official WMD designation would also open up new tools for prosecuting the illicit distribution of the drug.

"It's going to enable them to get moving on the ability to stop big shipments of it quicker and easier," the government consultant said.