John Bacon

USA TODAY

U.S. Ambassador Nikki Haley on Wednesday blamed Damascus and Moscow for the chemical weapons tragedy in Syria that killed dozens of women and children, warning the United States could take action if the United Nations fails to respond.

Haley, the U.S. envoy to the U.N., spoke at an emergency meeting of the Security Council. Hours later at the White House, President Trump said the attack "crossed a lot of lines for me" and "cannot be tolerated."

Neither Haley nor Trump discussed what action the U.S. might take.

The attack Tuesday killed more than 80 people and left hundreds more suffering from effects of the gas. Images of the tiny victims sparked global outrage against the government of Syrian President Bashar Assad.

Haley dismissed the Russian claim that a Syrian airstrike hit a rebel depot where chemical weapons were manufactured and stored, causing the chemical release. The attack "bears all the hallmarks of the Assad regime," Haley said.

"Yesterday morning we awoke to pictures (of) children foaming at the mouth, suffering convulsions, being carried in the arms of desperate parents," she told the Security Council while holding up graphic images. "We saw rows of lifeless bodies, some still in diapers, some showing scars of a chemical weapon attack."

Haley blasted Russia for supporting Assad, and said the U.S. might be compelled to act if the United Nations fails to do so.

"How many children have to die before Russia cares?" Haley asked.

Read more:

'Reprehensible': World reacts to horror of Syrian gas attack that killed children

Why Syria's Assad stays in power—even after chemical attacks

How Syria's civil war morphed into a struggle among global powers

The proposed Security Council resolution would condemn the use of chemical weapons and press Syria to provide immediate access for investigators to air bases from which attacks involving chemical weapons may have been launched. The Kremlin said the resolution is flawed because it assumes Damascus is to blame.

Britain and France called for the U.N. meeting, and both chastised Russia for standing by Assad.

"There is only one air force that has used such weapons in Syria," British envoy Matthew Rycroft told the Security Council. "This doesn't look like the work of terrorists. This doesn't look like the work of militants. This carries all the hallmarks of the Assad regime."

Syrian deputy U.N. ambassador Mounzer Mounzer rejected claims that his government used chemical weapons and accused rebel groups of using civilians as humans shields. Deputy Russian ambassador Vladimir Safronkov called for a "geographically balanced" fact-finding mission after complaining about the West's relentless "anti-Damascus campaign which hasn’t yet reached the place it deserves on the landfill of history."

Maj. Gen. Igor Konashenkov earlier told Russia’s TASS news agency the strike hit a depot containing mines loaded with chemical weapons on the outskirts of the rebel-held town of Khan Sheikhoun, where the deaths occurred.

Rycroft countered that claim. “We have every indication that this was a sustained attack using aircraft over a number of hours,” he told the council. “We see all the signs of an attack using a nerve agent.”

U.N. High Representative for Disarmament Affairs Kim Won-soo opened the Security Council meeting by saying that if the attack is proven to be chemical, it would be the most severe in Syria since hundreds of people were killed in rebel-held suburbs of Damascus in 2013.

The U.S. and Russia reached an agreement in 2013 to destroy Syria's chemical weapons arsenal. Still, the United Nations issued a report last year accusing Syria of using internationally banned toxic chemical weapons on civilians in 2014 and 2015.

The Syrian Observatory for Human Rights, a U.K.-based monitoring group, said 86 people were killed, including 30 children and 20 women. Syrian opposition health minister Firas Jundi put the death toll at more than 100 civilians and said 500 others, mostly children, were sickened or injured by the gas.

A Doctors Without Borders medical team providing support to the emergency department of Bab Al Hawa hospital in Idlib confirmed patients’ symptoms were consistent with exposure to a neurotoxic agent such as sarin gas, the group said Wednesday.

Pope Francis also weighed in, saying he “strongly deplored the unacceptable massacre" “and was "watching with horror the latest events in Syria.”

Contributing: Jane Onyanga-Omara