In a Feb. 25 incident, residents and medical staffers in a rebel-held Damascus suburb, Eastern Ghouta, described symptoms associated with chlorine exposure. One child died, medical staffers reported.
The president discussed potential actions early last week at a White House meeting that included Chief of Staff John F. Kelly, national security adviser H.R. McMaster and Defense Secretary Jim Mattis, officials said.
One official, who like others spoke on the condition of anonymity to address internal deliberations, said that the president did not endorse any military action and that officials decided to continue monitoring the situation.
Dana White, chief Pentagon spokeswoman, denied that Mattis took part in discussions about military action in Syria and said the “conversation did not happen.”
One senior administration official said that Mattis was “adamantly” against acting militarily in response to the recent chlorine attacks and that McMaster “was for it.”
The prospect of renewed military action, even if tabled for now, underscores the explosiveness of a conflict that has become a battlefield for rivalries between Russia and Iran on one side and the United States and its allies on the other.
The White House discussions come amid a drumbeat of accusations from Trump administration officials, who have sought to galvanize international pressure on Syria over repeated small-scale chemical attacks amid an escalation of widespread conventional air and ground assaults that have killed hundreds of civilians in recent weeks.
On Monday, the Assad government allowed a U.N. aid convoy to deliver food and other aid, but not certain medical supplies, to Eastern Ghouta, even as shelling and airstrikes continued.
The Trump administration has condemned Iran for deploying weapons and fighters that have helped turn the war in Assad’s favor. It has also blamed Russia for failing to enforce a U.N.-backed cease-fire proposal and for allowing the use of chemical weapons to continue.
“The civilized world must not tolerate the Assad regime’s continued use of chemical weapons,” White House press secretary Sarah Huckabee Sanders said in a statement Sunday.
Russian and Syrian officials have rejected reports of government chemical weapons use.
Images of Syrians suffering the effects of chemical exposure appear to have energized the president to explore launching a new assault, as they did before the missile attack he authorized on a Syrian air base in April.
Trump ordered the Pentagon to fire Tomahawk missiles on the Syrian facility believed to be linked to a sarin gas attack that killed 80 people. It was the first direct American assault on the Assad government, a step that President Barack Obama had shied away from, even after an estimated 1,400 people were killed in a gruesome attack in August 2013.
Administration officials say Syria has continued to make and employ chemical weapons despite an internationally backed deal to remove its stockpiles after the 2013 incident.
According to the Syrian American Medical Society (SAMS), which tracks reports from medical staffers, patients have reported symptoms linked to chlorine exposure seven times this year. In November, also in Eastern Ghouta, hospitals described seeing patients with symptoms indicative of sarin, the society said.
Unlike with earlier deadly incidents, U.S. officials say, the Assad regime is now conducting only small-scale attacks and is relying mainly on chlorine, which is made from commercially available materials and is more difficult to detect than nerve agents such as sarin.
“They clearly think they can get away with this if they keep it under a certain level,” a senior administration official told reporters last month.
Officials also suspect Syria of using ground-based systems rather than aerial means for delivering chemical agents, because they are harder to track.
The Syrian government has resorted to such attacks, officials say, to compensate for manpower shortages and to discourage supporters of the opposition from returning to strategic areas.
Even as the U.S. military winds down its campaign against the Islamic State, the Trump administration risks being more deeply drawn into Syria’s civil war, in which NATO ally Turkey is another important player. Many U.S. officials say that only greater political stability can prevent the extremists’ return.
The Pentagon has sought to keep its mission in Syria tightly focused on the Islamic State. There are about 2,000 U.S. troops in the east and north, tasked with advising local forces who have been battling the extremists.
Some officials also have raised concerns about conclusively assigning responsibility for chlorine attacks. Others express skepticism that another strike would deter Assad when the last one did not.
But other officials, particularly at the White House and the State Department, appear more open to renewed action against Assad. They say that a U.S. response might deter the Assad regime from rebuilding its chemical arsenal in a way that might eventually threaten the United States and might demonstrate that the United States will not be deterred by Russia’s presence in Syria.
The discussions highlight the gray area that chlorine has occupied in the West’s response to chemical weapons use in Syria. While chlorine is not a banned substance, its use as a choking agent is prohibited under international chemical weapons rules.
The Assad government’s reported employment of chlorine has been much less lethal than that of sarin, at least in recent reported incidents in Syria. SAMS said two people had been killed in the seven attacks this year.
Mattis told reporters last month that the United States was seeking evidence of renewed sarin use.
Fred Hof, an Obama administration official who is now at the Atlantic Council, said the United States would send a “deadly” message if it lashes out after chemical attacks but does nothing when civilians are killed with conventional arms.
“When we go out of our way to say, in effect, the only time we will lift a finger to protect Syrian civilians is when particularly deadly chemical weapons are employed, we are inadvertently — unintentionally but inevitably — encouraging the Assad regime, the Russians and the Iranians to attack civilians with everything at their disposal,” he said.
Even if Trump authorizes another attack, the Pentagon is likely to advocate limiting U.S. involvement in the war. The April attack, which included 59 cruise missiles, was aimed narrowly at an isolated airfield, minimizing the likelihood of tit-for-tat escalations.
The Organization for the Prohibition of Chemical Weapons is investigating whether chlorine was used in recent attacks in Eastern Ghouta, Reuters reported.
Greg Jaffe in Washington and Louisa Loveluck in Beirut contributed to this report.