Russia has called on the United States to reveal the list of the targets that it will attack in response to what it claims to be an upcoming chemical attack by the Syrian government.

Speaking at a Thursday United Nations Security Council meeting about the use of chemical weapons in Syria’s years-long war against foreign-backed militancy, Russia's UN envoy Vasily Nebenzya said Washington and its military allies, the UK and France had to reveal where they were going to attack.

"Reveal the list of targets, which, as was reported, the Pentagon has chosen for a possible airstrike by the three nations," he said.

"If you believe that those locations are related to the storage of chemical weapons, then show some respect to the international law and forward this information to the OPCW [Organization for the Prohibition of Chemical Weapons]," he added.

Syria and Russia have been preparing to mount an offensive on the northwestern province of Idlib, the last major stronghold of anti-government terrorists in the Arab country.

The White House has warned that the United States and its allies would not hesitate to respond “swiftly and vigorously” if the Syrian armed forces use chemical weapons in the upcoming offensive.

Nikki Haley, the US ambassador to the UN, said at the UNSC meeting that Russia and other members of the council should be in “deep shame” for siding with Syrian President Bashar al-Assad in the conflict.

"So we want to take this opportunity to remind Assad and his Russian and Iranian partners: you don’t want to bet against the United States responding again," she said, referring to Washington’s reaction to previous alleged chemical attacks in Syria.

Iran and Russia have both assisted Assad in purging terrorists from large parts of Syria.

The US has time and again accused Syria of carrying out chemical attacks against its own people.

Jim Jeffrey, who was named last month as US Secretary of State Mike Pompeo’s special adviser on Syria, echoed those remarks earlier in the day, saying there was “lots of evidence” that Damascus was preparing chemical weapons for the attack.

This is while both Russia and Syria have warned of suspicious activity in terrorist-controlled areas that show the anti-government militants are preparing to mount chemical attacks in Idlib and then blame it on the army.

Last year, when over 80 people died in the April 4 purported gas attack on Khan Shaykhun, US warships fired 59 Tomahawk cruise missiles from two warships in the Mediterranean Sea at the Shayrat airfield in Syria’s central province of Homs.

The attacks continued this year, when early on April 14, the US, Britain and France carried out a string of missile airstrikes against Syria over a suspected chemical attack against the Syrian town of Douma, near the capital Damascus.

Syria’s envoy to the UN, Bashar al-Jaafari, told the council that the three Western countries were among the main supporters of terror groups in the country.

The support, he argued, had hindered the political process in Syria over the past seven years.