WASHINGTON — Secretary of State Mike Pompeo pledged on Monday to ramp up the Trump administration’s diplomatic engagement with Asia in a speech that followed a blistering attack on the president’s trade policies by a usually stalwart Republican business ally.

Thomas J. Donohue, the longtime U.S. Chamber of Commerce president and chief executive, introduced Mr. Pompeo at an Indo-Pacific business forum by criticizing protectionist trade measures that he said led to both the Great Depression and World War II. He said American commitment to free trade since then had kept the peace around the world.

“If our companies lose access to foreign markets, they will struggle to remain competitive in the global economy,” Mr. Donohue said in a clear reference to President Trump’s trade war and tariffs. “Today, foreign policy is domestic policy.”

Mr. Pompeo spoke ahead of his travel to the region this week for a ministerial meeting in Singapore of the Association of Southeast Asian Nations, as well as bilateral meetings in Indonesia and Malaysia. The trip comes as Asian nations are moving away from the United States.