The US has warned Syrian President Bashar al-Assad and his government against another chemical attack on the country's civilians like the one carried out in April in the rebel-held Idlib province that left nearly 60 people dead and scores injured.

White House Press Secretary Sean Spicer said in a statement late on Monday (26 June) that the US has identified "potential preparations" by the Assad regime for another chemical attack in Syria. He warned that the Syrian government will have to pay "a heavy price" if another strike took place.

The US and its allies fighting Isis in the country had alleged that the 4 April chemical attack on Khan Sheikhoun town was ordered by the Assad regime, although the Syrian president denied the charges.

"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," Spicer's statement read, noting that the preparations were similar to the 4 April chemical attack.

"As we have previously stated, the United States is in Syria to eliminate the Islamic State of Iraq and Syria (Isis). If, however, Mr Assad conducts another mass murder attack using chemical weapons, he and his military will pay a heavy price," it added.

Soon after the White House statement, US Ambassador to the United Nations Nikki Haley warned that "any further attacks done to the people of Syria will be blamed on Asaad, but also on Russia and Iran who support him killing his own people".

In response to the previous chemical attack on 4 April, US President Donald Trump had ordered missile strikes on a Syrian air base suspected of launching the chemical weapons. US navy ships had fired 59 Tomahawk cruise missiles at Shayrat airfield, destroying aircraft and facilities at the base located in Syria's western Homs province. Syria was suspected of using banned toxic chemical sarin gas in the attack.

The US had also criticised Russia for the loss of innocent lives in Khan Sheikhoun as it did not stop ally Syria from conducting the deadly chemical attack. However, both Russia and Syria maintained that the toxic nerve agent was released when a Syrian air strike hit a rebel chemical weapons arsenal and munitions factory.