Islamic State (ISIS/ISIL) jihadists are “dead set” on using chemical weapons and are likely to try to use them in an attack as U.S.-backed Iraqi troops advance on Mosul, which is considered the terrorist group’s last major stronghold in Iraq, warned the Pentagon.

“We recognize this is real. They’re dead set on it. They would love to be able to use chemical weapons against us, against the Iraqis as they move forward,” U.S. Navy Capt. Jeff Davis, a Pentagon spokesman, told reporters Monday. “We are making every effort to make sure that we’re ready for it.”

Although the Islamic State launched chemical attacks in Iraq in March that exposed a child to an agent or agents that proved to be deadly and wounded hundreds of people, Davis downplayed the lethality of the jihadist group’s chemical weapons capabilities.

Noting that mustard gas used during World War I was far more deadly, he told reporters that the mustard agent used by the Islamic State is “not generally in a lethal concentration. It’s more of an irritant than anything else, but again, not something we view as militarily significant.”

Reuters noted, “The group typically uses a chemical powder bound together with oil, which leaves behind a telltale oil trace.”

In June, Gen. Bahram Arif Yassin, commander of Iraqi Kurdistan Regional Government (KRG) Peshmerga troops who have been targeted by Islamic State chemical attacks, noted in an exclusive interview with Breitbart News, “As Daesh [ISIS] loses ground, they are becoming more desperate and, as a result, we have seen an increase in chemical attacks across [Iraqi] Kurdistan.”

Davis’ warning that the Islamic State is intent on attacking the U.S. with chemical weapons comes a week after the terrorist group launched a chemical-laden rocket against U.S. troops at a base in northern Iraq. It failed to kill or hurt anyone. It was the first recorded chemical attack on the United States since the jihadist group conquered swaths of Iraq in 2014.

Davis said that the shell is undergoing additional tests. Initially, it tested positive for a potentially deadly sulfur-mustard blister agent, but two subsequent tests have been determined to be inconclusive.

Although the rocket landed several hundred yards from where hundreds of American troops were working to prepare an airfield for an upcoming Iraqi offensive to recapture the city of Mosul from the Islamic State, no one was killed or injured in the attack.

Mosul, Iraq’s second-largest city, is located in northern Iraq’s Nineveh province. The Islamic State has launched numerous chemical attacks in Syria and Iraq, including some that have been deadly. The majority of the ones in Iraq have occurred in the northern part of the country.

In March, the U.S. captured an Islamic State jihadist in Nineveh province who “specialized in chemical and biological weapons” under Saddam Hussein, reported the Associated Press (AP).

He was serving as the chief of the group’s “branch for the research and development of chemical weapons,” the report stated. The Islamic State chemical weapons emir warned that the terrorist group was planning to use the chemical weapons.

According to experts and Peshmerga troops in northern Iraq, the chemical weapons principally used by the Islamic State so far have been chlorine and sulfur mustard, which are considered poor weapons by modern standards.

Dlovan Shukry Essa, a Peshmerga fighter who had been charged with investigating possible chemical attacks against his counterparts in Iraqi Kurdistan, told Breitbart News that he was wholly unprepared to carry out his responsibilities.

He explained that the only tool at his disposal was an air-purifying gas mask that only covers part of the face and is “intended only for low hazard levels.”

On the other hand, Davis told reporters U.S. troops deployed to northern Iraq have the training and equipment necessary to defend against chemical attacks and are working to ensure the Iraqis are properly equipped, as well.

President Barack Obama has been reluctant to arm and supply the Iraqi Kurds directly, despite their successes on the ground. Peshmerga fighters must go through the central Iraqi government in Baghdad to get U.S.-supplied military equipment.

Under current law, the U.S. government is only allowed to send military equipment to governments of countries internationally recognized as sovereign — not to autonomous regions within countries like the KRG.

Davis reportedly said Monday that “the United States has provided more than 50,000 gas masks to Iraq, with about 40,000 going to Iraqi security forces.”

U.S.-led coalition airstrikes and special operations raids have been targeting the Islamic State’s chemical weapons infrastructure.

“An airstrike by the U.S.-led military coalition destroyed an Islamic State chemical weapons factory on Friday near Qayyara, the second attack against a chemical arms facility this month,” reported Reuters.