By Steve Holland and Michelle Nichols
WASHINGTON/UNITED NATIONS (Reuters) - U.S. President Donald Trump promised quick action on Monday in response to a "barbaric" suspected chemical weapons attack in Syria and made clear that all options including military action were on the table.
Speaking at a Cabinet meeting, Trump said he was meeting with military and other advisers and a decision would be made within 48 hours and might come as soon as the end of the day.
"Nothing is off the table," he said when asked if U.S. military action was a possibility.
The suspected chemical weapons attack late on Saturday killed at least 60 people, with more than 1,000 injured in several sites in Douma, a city near the capital, Damascus, according to a Syrian aid organization.
Two days later, the White House was still only able to say that the attack fit the pattern of Syrian President Bashar al-Assad's chemical weapon use.
Initial U.S. assessments have so far been unable to determine conclusively what materials were used in the attack and could not say with 100 percent certainty that Assad's government forces were behind it.
"It was an atrocious attack. Trump said. "This is about humanity. We're talking about humanity. It can't be allowed to happen," he said.
Asked if Russian President Vladimir Putin bore any responsibility for the attack, Trump said: "He may, yeah, he may. And if he does, it’s going to be very tough, very tough."
The U.S. envoy to the United Nations, Nikki Haley, said Washington "will respond" to the attack regardless of whether the U.N. Security Council acts or not.
The Syrian government and its ally Russia have denied involvement in the attack.
International bodies led by the Organisation for the Prohibition of Chemical Weapons (OPCW) were trying to establish exactly what happened in Douma, a rebel-held town in the eastern Ghouta district.
Britain and the United States agreed on Monday that the attack bore the hallmarks of previous chemical weapons attacks by Assad's government but neither country gave details of what kind of chemical might have been used or how the attack was staged.
"The images, especially of suffering children, have shocked the conscience of the entire civilized world," White House spokesman Sarah Sanders said. "Sadly, these actions are consistent with Assad's established pattern of chemical weapons use."
Trump said he was talking to military leaders and would decide who was responsible for the "barbaric act" - whether it was Russia, Assad's government, Iran, or all of them together.
A day earlier, the U.S. president who had sought warmer relations with Russia criticized Putin by name on Twitter as he castigated Russia and Iran for backing "Animal Assad."
Trump also said on Sunday after initial reports of an attack that there would be a "big price to pay."
The United States fired missiles on a Syrian air base a year ago in response to the killing of dozens of civilians in a sarin gas attack in an opposition-held town. The missile strikes did little long-term damage to Syrian government forces and Assad's position has only become stronger with Iranian and Russian support.
The stakes are higher for any new U.S. military action, with Trump explicitly mentioning Iran and Russia in connection with the weekend attack.
U.S. Defense Secretary Jim Mattis on Monday accused Russia of falling short on its obligations to ensure that Syria abandoned its chemical weapons capabilities.
Russia's U.N. envoy called for OPCW investigators to fly to Syria as early as Tuesday, saying Syrian and Russian troops would escort them to the area of the attack.
The OPCW did not immediately respond to a request for comment. But weapons inspectors are not expected to go to Syria after being attacked twice while tying to get to the sites of chemical weapons attacks since 2013.
Instead, they have in recent investigations gathered blood samples from victims and interviewed witnesses outside of Syria.
MONDAY AIR STRIKES
The Syria conflict was further complicated on Monday when unidentified war planes struck a Syrian air base near Homs, killing at least 14 people, including Iranian personnel. Syria and Russia accused Israel of carrying out the attack.
Israel, which has struck Syrian army locations many times in the course of its neighbor's 7-year-old civil war, has neither confirmed nor denied mounting the raid.
But Israeli officials said the Tiyas, or T-4, air base was being used by troops from Iran and that Israel would not accept such a presence in Syria by its arch foe.
The incidents in Douma and Tiyas demonstrated the complex and volatile nature of the Syria war, which involves a number of countries and a myriad of insurgent groups.
Assad now has the upper hand in the conflict, but any international action could delay his efforts to bring it to a close.
The U.S. State Department said on Monday that the Douma victims' symptoms were consistent with those caused by a nerve agent but they could not confirm what had been used.
It urged Russia and the Syrian government to allow international monitors access to the affected areas.
Britain said it was working with its allies to agree on a joint response to the attack. France said it would work closely with the United States on a response. Both countries agreed that responsibility for the strike must be established. Turkey also called for an investigation.
President Emmanuel Macron has issued warnings previously that France would strike if proof of lethal chemical attacks were established. But Paris stopped short of apportioning blame on Assad's forces for Saturday's attack.
Russian Foreign Minister Sergei Lavrov said such allegations were false and a provocation. Lavrov also said the strike on the T-4 base was a dangerous development.
The Russian military said on Monday its medics had examined patients in a hospital in Douma and had found no traces of a chemical attack, Interfax news agency reported.
Syrian government forces had launched an air and ground assault on Douma, the last town held by rebels in eastern Ghouta, on Friday.
The Union of Medical Care Organizations (UOSSM) said at least 60 people had been killed by the alleged chemical attack.
"The numbers keep rising as relief workers struggle to gain access to the subterranean areas where gas has entered and hundreds of families had sought refuge," it said.
One video shared by activists showed bodies of about a dozen children, women and men, some with foam at the mouth. Reuters could not independently verify the reports.
The OPCW, based in The Hague, opened an investigation on Monday to determine whether dozens of people were gassed to death in the attack.
Dr. Muhammad, a doctor in Ghouta quoted by UOSSM, said patients were coughing blood, a symptom not seen in previous chemical attacks.
U.N. war crimes investigators had previously documented 33 chemical attacks in Syria, attributing 27 to the Assad government, which has repeatedly denied using the weapons.