ERBIL, Kurdistan Region – America will “respond very strongly” if the Syrian regime uses chemical weapons in Idlib, US President Donald Trump's national security adviser John Bolton told reporters in Jerusalem on Wednesday. 

“We now see plans for the Syrian regime to resume offensive military activities in Idlib province,” Bolton told a press conference.

“We are obviously concerned about the possibility that Assad may use chemical weapons again. Just so there’s no confusion here, if the Syrian regime uses chemical weapons we will respond very strongly and they really ought to think about this a long time.”

Five years after the chemical weapons attack on Ghouta drew global condemnation, three permanent members of the UN Security Council vowed to act if Bashar al-Assad’s forces use such weaponry to retake Idlib – the last rebel holdout. 

In a joint statement issued on Tuesday – the fifth anniversary of the sarin attack that killed more than 300 people – the three powers said they are “gravely concerned” about the humanitarian consequences of the regime’s impending offensive on Idlib. 

“We also underline our concern at the potential for further – and illegal – use of chemical weapons,” the three nations said.

Western powers did not act against Assad at the time, despite then-President Barack Obama calling the use of chemical weapons a “red line” which, if crossed, would lead to armed intervention. Instead, Russia intervened to negotiate the surrender of Syria’s chemical weapons. 

However, Assad was again accused of using chemical weapons against civilians in rebel-held Douma in April this year, prompting the US, UK, and France to launch missile strikes against three government facilities. 

“As we have demonstrated, we will respond appropriately to any further use of chemical weapons by the Syrian regime, which has had such devastating humanitarian consequences for the Syrian population,” the three states said in their statement. 

“We remain resolved to act if the Assad regime uses chemical weapons again.”

“Our position on the Assad regime’s use of chemical weapons is unchanged,” the statement added.

Having retaken the suburbs of Damascus from the armed opposition, and regained control over Daraa – the cradle of the 2011 uprising that morphed into Syria’s seven-year civil war – Assad has now set his sights on the country’s northern provinces.

Idlib, which straddles the Turkish border, is mostly under the control of Hay’at Tahrir al-Sham (HTS) – an umbrella group of jihadists led by Al-Qaeda’s former Syrian affiliate. Pockets of the province remain under ISIS control. 

Complicating matters, the Turkish armed forces also have several outposts in Idlib in support of rebel groups. Moves by Assad risk pitting Russian-backed Syrian forces against Turkish soldiers. 

Assad’s forces have already begun massing in the areas of Idlib already under its control and on its southern and eastern flanks. 

It is unclear when the offensive will formally begin and what impact the fall of Idlib could have on Turkish-controlled Afrin and the northern provinces controlled by the Kurdish-led Syrian Democratic Forces (SDF). 

Last updated 12.06 p.m.