Story highlights After a chemical attack on a rebel-held town in April, the US retaliated with a missile strike

Trump said in April it was in the "vital national security" of the US to prevent use of chemical weapons

(CNN) The White House has warned there are "potential preparations for another chemical weapons attack" by the Syrian regime and told the country's president, Bashar al-Assad, he would face a "heavy price" if one is carried out.

The announcement comes amid rising tensions in Syria between the US-led coalition and Russia, which is backing the Assad regime.

The US launched a fierce riposte in the aftermath of the chemical attack launched by Assad's forces in April -- which was condemned across the world -- and says it will not hesitate to take action should another similar strike take place. Assad dismissed allegations of the chemical attack as "100% fabrication."

Photos: Suspected chemical attack in Syria Hide Caption 1 of 11 Photos: Suspected chemical attack in Syria This photo, provided Tuesday, April 4, by the activist Idlib Media Center, shows dead children after a suspected chemical attack in the rebel-held city of Khan Sheikhoun, Syria. Dozens of people were killed, according to multiple activist groups. Hide Caption 2 of 11 Photos: Suspected chemical attack in Syria A man carries a child at a makeshift hospital in Khan Sheikhoun. Activists have blamed the Syrian regime for the attack. In an apparent reference to the attack, two state-run Syrian media outlets reported that there was an explosion at a "rebel poison gas factory" in the countryside of Idlib province. The government has denied using chemical weapons in the past. Hide Caption 3 of 11 Photos: Suspected chemical attack in Syria A child's body is seen in Khan Sheikhoun. Hide Caption 4 of 11 Photos: Suspected chemical attack in Syria In this photo provided by the Idlib Media Center, doctors treat a child after the suspected attack. Hide Caption 5 of 11 Photos: Suspected chemical attack in Syria A baby's dead body is covered. Many of the casualties came as a result of asphyxiation, local doctors say. Hide Caption 6 of 11 Photos: Suspected chemical attack in Syria A dead baby is seen in the aftermath of the attack. "I've never seen anything like it, beyond description," said Fares al-Jundi, a doctor who spoke with CNN. He lives in a nearby village and rushed to the hospital after the airstrikes. Hide Caption 7 of 11 Photos: Suspected chemical attack in Syria Al-Jundi described how whole families were killed: They died of asphyxiation, and foam covered their mouths. Many died suddenly. "I believe this horrible memory will stay with me for the rest of my life," al-Jundi said. Hide Caption 8 of 11 Photos: Suspected chemical attack in Syria An unconscious Syrian child receives treatment at a hospital in Khan Sheikhoun. Hide Caption 9 of 11 Photos: Suspected chemical attack in Syria This photo provided by the Idlib Media Center shows victims of the suspected attack. Hide Caption 10 of 11 Photos: Suspected chemical attack in Syria Civil defense workers try to reduce the effects of toxic gas as they carry out search-and-rescue missions in Khan Sheikhoun. Hide Caption 11 of 11

"The United States has identified potential preparations for another chemical weapons attack by the Assad regime that would likely result in the mass murder of civilians, including innocent children," according to a White House statement released Monday night.

"The activities are similar to preparations the regime made before its April 4, 2017 chemical weapons attack," the statement added. "As we have previously stated, the United States is in Syria to eliminate the Islamic State of Iraq and Syria. If, however, Mr. Assad conducts another mass murder attack using chemical weapons, he and his military will pay a heavy price."