Mike Pompeo has Trump's ear, but who really wields the influence?

America’s top diplomat swept through the grandiose lobby of the famed Peninsula Hotel with purpose early on a recent morning.Secretary of State Mike Pompeo couldn’t have slept much since arriving late the night before, but he had a bounce in his step as a clutch of reporters attempted to follow him into a small room where top Philippine business leaders were waiting to have breakfast with him.

Cameras flashed and elbows jostled among the journalists craning for a glimpse of who was in the room as the secretary took his seat. Then came an awkward silence before Mr. Pompeo suddenly waved a hand toward the reporters and said, “I’ll wait for these nice people to leave before we get started.”

The comment delighted the assembled business leaders, whose nervous laughter offered a rare glimpse into a behind-the-scenes world where sources close to Mr. Pompeo say he is most comfortable and effective — a world where he has carved out a reputation for frank talks with foreign counterparts, especially capitalists.

In an administration that even close allies such as the Philippines have trouble assessing, Mr. Pompeo’s clout and evident camaraderie with his boss, President Trump, have made him a reassuring and consequential figure. He is the one heavyweight other than Vice President Mike Pence who has held top-level Cabinet status for Mr. Trump’s entire presidency.