Kerry said on Friday that Russian and Syrian government actions in Aleppo "beg for a war-crimes investigation." Reuters US Secretary of State John Kerry called for a war-crimes investigation of Russia and Syria over their bombardment of hospitals, civilian infrastructure, and aid workers' headquarters in Syria's largest city, Aleppo.

The Russian and Syrian bombing campaign in Aleppo "begs for a war crimes investigation," Kerry said on Friday during a press conference with French Foreign Minister Jean-Marc Ayrault.

Ayrault had just arrived in Washington, DC, from Moscow, where he met with Russian officials, according to the Associated Press.

Russia and Syrian President Bashar Assad "owe the world more than an explanation" for their attacks on hospitals in Aleppo, Kerry said, adding that the attacks are "way beyond" accidental at this point.

He accused Russia and Assad of employing a "targeted strategy ... to terrorize civilians." "We look forward today to a very frank discussion about what potential next steps are," Kerry said. "We intend to jointly figure out how best to be able to deliver the strongest message possible about the actions that might be taken to deal with this bombing of Aleppo, this siege, in the 21st century, of innocent people." Both Syria and Russia are signatories to the Geneva Conventions, which establish protections for civilians and soldiers during war. The Fourth Geneva Convention stipulates that civilians who find themselves in the hands of a party to the conflict (or occupying power of which they are not nationals) — otherwise known as "protected persons" — "shall not have anything done to them of such a character as to cause physical suffering or extermination." Kerry said that the UN Security Council vote on a draft resolution to reinstate a ceasefire in Syria, set to take place on Saturday, would be a "moment of truth" for Moscow. Russia indicated that it would not be approving the resolution, which calls on the UN to monitor a new truce and threatens to "take further measures" against any party in Syria that violates it, Reuters reported. "This is not a draft which is right for adoption, I have this suspicion that the real motive is to cause a Russian veto," Russia's ambassador to the UN, Vitaly Churkin, said on Friday. "I cannot possibly see how we can let this resolution pass."

Kerry's statement came after weeks of harsh diplomatic jabs between Moscow and Washington over the Russia-backed government offensive on Aleppo.

"What Russia is sponsoring and doing is not counterterrorism — it is barbarism," Samantha Power, the US ambassador to the UN, told member nations during a Security Council meeting late last month.

Kremlin spokesman Dmitry Peskov quickly hit back, calling Powers' language "unacceptable." During the turbulent meeting, Russia's ambassador to the UN, Vitaly Churkin, doubled down on an oft-repeated talking point: Russian airstrikes are targeting only terrorists.

On Monday, the US decided to suspend ties with Moscow over Russia's role in the Syrian government's scorched-earth offensive on Aleppo. The offensive has killed hundreds of civilians and opposition fighters in the city's rebel-held east over the past two weeks, spawning an "increased mood in support of kinetic actions against the regime," a senior administration official told The Washington Post this week.

In response, Russia suspended a nuclear and energy-related research pact with the US and deployed surface-to-air missiles to its naval base in Tartus, on Syria's western coast.

Gen. Igor Konashenkov, a Russian Defense Ministry spokesman, suggested in a statement released on Thursday that Russia would fire on any aircraft taking offensive action near Russian troops even before identifying them, leaving open the possibility that Russia would attack US aircraft.

A medic holds a dead child after airstrikes in the rebel-held Karam Houmid neighborhood in Aleppo, Syria, on October 4, 2016. REUTERS/Abdalrhman Ismail "Any missile or airstrikes on the territory controlled by the Syrian government will create a clear threat to Russian servicemen," the statement read. "Russian air defense system crews are unlikely to have time to determine in a 'straight line' the exact flight paths of missiles and then who the warheads belong to."

Russian lawmakers also approved a measure on Friday that would allow Russian troops to remain stationed in Syria indefinitely.

Russia accused the US of "blatant aggression" after US warplanes targeted a Syrian army base on Al-Tharda mountain on September 17, killing as many as 80 Syrian troops. The Obama administration said the airstrike was meant to target the Islamic State.