Here's a look at the argument over Israel's use of lethal force against Palestinians protesting at the border fence.
The president holds individual conversations with French and British leaders. The White House says the three nations agreed the assault on Syria was "successful and necessary to deter" the future use of chemical weapons.
The U.S., U.K. and France acted in the awareness that Russian and Syrian forces may already have tried to clean up important evidence in Douma, where dozens died in last weekend's attack.
But Syrian allies Russia and Iran call the use of force by Western allies a "military crime" and "act of aggression" with the potential to worsen a humanitarian crisis.
Chancellor Angela Merkel says her nation will not engage in a military strike against the Assad regime, but she backs unspecified actions that would "send a signal" that use of chemical weapons is intolerable.
Mike Pence will attend the 8th Summit of the Americas in Lima, Peru, this week, as the president oversees the U.S. response to Syria's apparent chemical weapons attack on civilians.
The poisoning of Sergei Skripal by what authorities believe was a military-grade nerve agent has chilled relations between Russia and the West, producing an unprecedented wave of diplomatic expulsions.
Syria's U.N. ambassador says that following the government takeover of Hamouria from "terrorists," the government is helping evacuate civilians "who were taken as human shields."
White House spokeswoman Sarah Huckabee Sanders says Syria is "terrorizing hundreds of thousands of civilians" with airstrikes, artillery, rockets and "a looming ground attack."