PARIS—The Obama administration worked to sell its Syrian disarmament deal to skeptical allies overseas and domestic critics at home, stressing force remains an option against President Bashar al-Assad, but that there is still time for diplomacy to work.

Secretary of State John Kerry set off on a globe-hopping mission in search of support, meeting with Israeli Prime Minister Benjamin Netanyahu in Jerusalem on Sunday ahead of meetings with European and Middle Eastern allies in Paris on Monday.

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