WASHINGTON — On his first foreign trip since becoming president, Donald Trump will travel this month to Saudi Arabia, Israel and Rome, in what the White House described as an effort to rally the world — and the three major faiths symbolized by those locales — together to battle intolerance that has given rise to extremist groups such as the Islamic State (IS).

The itinerary reflects what White House officials described as a way to translate Trump’s “America First” agenda into confident American leadership on the world stage, to reinvigorate old alliances and seek new opportunities for cooperation.

White House officials, in describing the thinking behind the trip, offered a fascinating glimpse into how they see Trump conducting foreign policy largely through building personal relationships and conducting personal diplomacy, and as someone who is ideologically flexible, and not doctrinaire, and willing to adjust plans as the facts change. They also said they have come to see his perceived unpredictability on foreign policies as being an asset that keeps allies and foes alike slightly uncertain.

“Good if they are nervous,” one official described the advice he was given after Trump was elected about countries not knowing what Trump’s foreign policy positions would be.