TEHRAN, Young Journalists Club (YJC) -President Vladimir Putin's spokesman, Dmitry Peskov, said "such threats to Syria's legitimate leaders are unacceptable."
The Russian official also denounced the administration of US President Donald Trump for using the phrase "another chemical weapons attack."
Elsewhere in his remarks, Peskov said an independent probe into an attack in April was never conducted despite Russia's calls for one, adding, "That is why we do not think it is possible to lay the blame on the Syrian armed forces."
In Moscow on Tuesday, a senior Russian lawmaker dismissed the latest US warning as "provocation."
Frants Klintsevich, the first deputy chairman of the defense and security committee in the upper chamber of the Russian parliament, accused Washington of "preparing a new attack on the positions of Syrian forces."
"Preparations for a new cynical and unprecedented provocation are underway," Klintsevich said.
Damascus: US claims foreshadow "diplomatic battle" against Syria
Meanwhile, Syria has denied US allegations, saying it has never used chemical weapons in its war against foreign-backed terrorist groups.
Ali Haidar, the Syrian minister for national reconciliation, said on Tuesday that the White House statement foreshadowed a "diplomatic battle" that would be waged against Syria in the halls of the United Nations.
The White House accused the government in Damascus of preparing to carry out a chemical attack in the Arab country.
In an ominous statement issued with no supporting evidence or further explanation, US Press Secretary Sean Spicer claimed on Monday night that the United States had “identified potential preparations” for an attack “that would likely result in the mass murder of civilians, including innocent children.”
Spicer said Syrian President Bashar al-Assad and the Syrian military would “pay a heavy price” if they went ahead with the alleged plan.
The White House claimed it had detected activity resembling the buildup to a chemical weapons attack on April 4.
The Associated Press, meanwhile, cited anonymous US State Department officials who would “typically” be consulted before such statements are made as saying that they had been caught “completely off guard” by Spicer’s statement and that they had come to know about it only after it was released.
The AP report also said that the content of Spicer’s statement “didn’t appear to be discussed in advance with other national security agencies.”
On April 4, over 80 people died in an incident involving chemicals in the town of Khan Shaykhun in the western province of Idlib in Syria. Some Western countries blamed the Syrian government for what they said had been a chemical attack, and days later, the United States used it as a pretext to fire 59 Tomahawk cruise missiles at a Syrian airfield in the central province of Homs. US officials claimed that the alleged Khan Shaykhun gas attack had been launched from the airfield.
Syria said it had not used chemical weapons and blamed foreign-backed militant groups for stockpiling the chemicals.
Damascus and its ally Moscow said the Syrian government had conducted a conventional airstrike on the positions of terrorists in Khan Shaykhun, which also targeted a chemical arms depot held and run by anti-Damascus militants, causing a leakage of the toxic substance and the deaths.
Veteran American investigative journalist Seymour M. Hersh recently confirmed the Syrian narrative. He said Trump turned a blind eye to reports by the US intelligence community that warned there was no evidence suggesting the Syrians had used chemical weapons. The US intelligence had found that the Syrians had on April 4 targeted a meeting site of militants, using a Russian-supplied guided bomb equipped with conventional explosives.
Russia has been lending its air power to Syria’s counterterrorism operations since September 2015. Iran has also been providing the Syrian military with advisory military support. The collective support has helped Syria rid considerable territory of Takfiri presence and helped establish an all-out ceasefire in the Arab country in late 2016.
Moscow has already suspended a military hotline with Washington over another provocative incident that saw US forces shoot down a Syrian fighter jet.
The ratcheting up of tensions by the US, including the latest statement, now risks sparking a major confrontation between parties to the conflict in Syria and complicating efforts aimed at resolving it.
The United States has unsanctioned presence in Syria.
In a recent phone call initiated by US Secretary of State Rex Tillerson, Russian Foreign Minister Sergei Lavrov called on the United States to prevent “provocations” against Syrian government forces.
The Russian Foreign Ministry said on Monday that Lavrov “called on Washington to take steps to prevent provocations against Syrian government forces carrying out operations against terrorists.”