The warning came amid signs that Syrian President Bashar Assad was preparing an offensive in Idlib province Mattis says there is ‘zero intelligence’ that opposition fighters have such capability WASHINGTON: The US warned Syria Tuesday it will respond “swiftly and appropriately” if it uses chemical weapons against its people. The warning came amid signs that Syrian President Bashar Assad was preparing an offensive in Idlib province that the UN has said poses the threat of a humanitarian disaster. “Let us be clear, it remains our firm stance that if President Bashar Assad chooses to again use chemical weapons, the United States and its allies will respond swiftly and appropriately,” White House Press Secretary Sarah Sanders said in a statement. The White House was “closely monitoring the situation in Idlib province, Syria, where millions of innocent civilians are under threat of an imminent Assad regime attack, backed by Russia and Iran,” Sanders said. “President Donald J. Trump has warned that such an attack would be a reckless escalation of an already tragic conflict and would risk the lives of hundreds of thousands of people,” she added. Separately, US Defense Secretary Jim Mattis said there was “zero intelligence” of chemical weapons capabilities possessed by groups opposing Assad in Idlib, adding that the facts did not back Russian assertions. In the past few days, Russian officials, cited by Russian media, have said there was a plan by “militants” to stage a false chemical weapons attack in Idlib province to frame Assad. “We have zero intelligence that shows the opposition has any chemical capability,” Mattis told reporters traveling with him to the Indian capital of New Delhi. Russia"s Ambassador to the US Anatoly Antonov said he had told US officials that Moscow was concerned over signs the US was preparing new strikes on Syria and warned against “groundless and illegal aggression against Syria.” “We have made very clear that by putting out innuendo that somehow any chemical weapon use coming up in the future could be ascribed to the opposition, well, we want to see the data,” Mattis said. “We cannot see anything that indicates the opposition has that capability.” He said instead there was a history of Assad"s regime using such weapons. US President Donald Trump has twice ordered US-led strikes against targets in Syria in response to what Washington called the Assad regime’s use of chemical weapons against civilians. Asked if he saw indications of the Syrian regime preparing to use chemical weapons in Idlib, Mattis said, “I think the best answer to that is, we are very alert.” Sputnik, a Russian state-owned news outlet, said recently the White Helmets rescue service had delivered a large shipment of toxic substances to “local armed militant groups.” The Pentagon said the Russian government was using a “concentrated disinformation campaign” to discredit the US and its allies. “That Russia is seeking to plant false lies about chemical weapons use suggests that Moscow is seeking to deflect from its own culpability when these heinous weapons are used,” Commander Sean Robertson, a Pentagon spokesman, said in a statement.