The White House warned Syrian dictator Bashar al-Assad that if he uses chemical weapons again, he will face another response from President Donald Trump.

“As we have previously stated, the United States is in Syria to eliminate the Islamic State of Iraq and Syria,” a statement from White House Press Secretary Sean Spicer said. “If, however, Mr. Assad conducts another mass murder attack using chemical weapons, he and his military will pay a heavy price.”

Spicer announced that the United States identified “potential preparations” for another attack using chemical weapons, predicting that it would attack civilians, including children.

“The activities are similar to preparations the regime made before its April 4, 2017 chemical weapons attack,” the statement read. The statement was released Monday night.

In April, the president approved an attack in Syria of 59 Tomahawk missiles after intelligence showed that Assad had launched chemical weapons against civilians.

“It is in this vital national security interest of the United States to prevent and deter the spread and use of deadly chemical weapons,” Trump said afterwards, justifying his use of force against Syria. The president added that “beautiful babies” had been killed in the “barbaric attack.”

“No child of God should ever suffer such horror,” he added.

The U.S. military increased attacks in Syria in recent weeks, shooting down Iranian-built drones and a Syrian Air Force Su-22.

Tensions with Russia have also increased, after they warned that “any aircraft” operating west of the River Euphrates would be treated as “targets.”

Despite the warnings, the White House affirmed their right to self defense.

“The escalation of hostilities among the many factions that are operating in this region doesn’t help anybody. The Syrian regime and others in the regime need to understand that we will retain the right of self-defense, of coalition forces aligned against ISIS,” Spicer said in June.