The US on Monday accused Russia of having known about and trying to cover up the April 7 chemical attack in Syria, while Russia threatened "real war" with the US and its allies if the US sanctioned it over its ties to Syrian President Bashar Assad's regime, which is believed to be responsible for the attack.
The Associated Press reported on Monday that US officials said a Russian-made fighter jet bombed a hospital where victims of the attack, which killed 87 people, sought treatment. The officials believe it was an attempt to cover up the use of chemical weapons.
It's unclear what actions the US may take toward Russia if it believes Russia was complicit in the regime's use of chemical weapons.
Earlier Monday, Russia suggested that if G-7 nations — which include France, Canada, the UK, and Japan — delivered an "ultimatum" involving increasing sanctions, it could result in "real war" between the US and its allies and Russia.
Experts have told Business Insider that while the US and EU have sanctions on the books punishing Moscow for its actions in Ukraine, additional sanctions targeting Russia's energy exports could cripple the military powerhouse.
Russia also warned that more US strikes on Syria would be met with force. The US last week fired 59 cruise missiles at the airfield in Syria where the chemical attack is believed to have been launched.
The US's ambassador to the UN, Nikki Haley, has said that the US is "prepared to do more" in Syria, though she also said, "We hope that will not be necessary."
"What America waged in an aggression on Syria is a crossing of red lines," Russia's foreign ministry said in a statement. "From now on, we will respond with force to any aggressor or any breach of red lines from whoever it is, and America knows our ability to respond well."
Russia and Syria have both denied culpability in the chemical attack on April 4, saying their jets bombed a rebel base that contained the "toxic substances" that killed nearby civilians.
But experts say the components of sarin gas, which they believe was used in the attack, are stored separately and that the nations' explanation does not stand up to scrutiny.
After the US's strike, Russia reportedly suspended key military agreements with the US that were meant to reduce the risk of war by coordinating air traffic in Syria's congested airspace and keeping open a deconflicting channel, where incidents can be discussed before militaries escalate the situation.
However, US Secretary of State Rex Tillerson told CBS's "Face the Nation" on Sunday, "As far as I know, the line of communication continues to be open, and the battlefield commanders are able to communicate with one another."
Airstrikes and traffic over Syria have also continued at a regular pace, with US-backed forces bombing ISIS targets near Raqqa and Syrian warplanes taking off less than 24 hours after the US hit the Sharyat airfield.
SEE ALSO: US official: Russia knew in advance that Syria would launch chemical weapons attack
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