Syria has denied the Trump administration's charge that it may be planning "another chemical weapons attack," which the White House said "would likely result in the mass murder of civilians."
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The White House did not provide specific evidence to support the allegation, which the government of President Bashar al-Assad has dismissed, according to The Associated Press.
Ali Haidar, the Syrian minister for national reconciliation, rejected the White House statement, telling the AP that the charges against Assad's regime pointed to "a new diplomatic campaign against Syria at the U.N."
In a statement released Monday evening, White House press secretary Sean Spicer said the United States found "potential" evidence that Assad was preparing to conduct an attack similar to one carried out April 4 that killed dozens of civilians, including children.
"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," the statement said. "The activities are similar to preparations the regime made before its April 4, 2017, chemical weapons attack."
"If ... Mr. Assad conducts another mass murder attack using chemical weapons, he and his military will pay a heavy price," the statement warned.
The strong wording of the White House statement drew a reaction from Russia, a key ally and military partner of Assad's government.
"We do not know what is the basis for this," Kremlin spokesman Dmitry Peskov told reporters today. "And of course, we categorically disagree with the 'another attack' wording."
"We also consider any similar threats to the legitimate leadership of the Syrian Arab Republic unacceptable," he added.
The April 4 attack, which killed at least 70 people in the rebel-held territory of Idlib province, prompted President Trump to order a cruise missile strike on a Syrian government-controlled air base. The Assad regime denied responsibility for the attack.
The strike was the United States' first direct assault on the Syrian government and was one of Trump's most dramatic military orders since taking office.
"Any further attacks done to the people of Syria will be blamed on Assad, but also on Russia and Iran who support him killing his own people," Haley tweeted late Monday.
Any further attacks done to the people of Syria will be blamed on Assad, but also on Russia & Iran who support him killing his own people.— Nikki Haley (@nikkihaley) June 27, 2017
Assad, meanwhile, is touring Syria. He visited a Russian air base in Latakia, according to images published by the Syrian state-run news agency SANA.
In the photos, he can be seen shaking hands with Russian military staffers and climbing into a Russian fighter jet.
ABC News' Katherine Faulders contributed to this report.