Under plan, troops would replace American military contingent after ISIS defeat and help secure country’s north; proposal faces challenges. WASHINGTON—The Trump administration is seeking to assemble an Arab force to replace the U.S. military contingent in Syria and help stabilize the northeastern part of the country after the defeat of Islamic State, U.S. officials said. John Bolton, President Donald Trump’s new national security adviser, recently called Abbas Kamel, Egypt’s acting intelligence chief, to see if Cairo would contribute to the effort, officials said. The initiative comes as the administration has asked Saudi Arabia, Qatar and the United Arab Emirates to...