Duterte voiced outrage at comments made the previous day by the top US envoy to Asia that his fiery rhetoric and crime war, which has claimed about 3,700 lives in four months, were bad for business.
"These Americans are really crazy. Their style is to walk here. They think they are somebodies," Duterte said, as he held up a newspaper with headlines reporting the criticism from US assistant secretary of state Daniel Russel.
Duterte then flew to Japan, one of the top US allies in Asia, for a three-day visit that is partly aimed at building on two-way trade of more than $18 billion dollars last year.
"With Japan as the Philippines' top trading partner, I shall seek the sustainment and further enhancement of our important economic ties," Duterte, 71, said in prepared remarks at Manila airport.
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"I look forward to meeting business leaders in Japan. I will tell them clearly that the Philippines is open for business."
More than 100 of them waiting outside gave him an enthusiastic welcome, calling his name and waving small Philippine flags. A smiling Duterte approached them and shook hands.
Duterte will meet with Prime Minister Shinzo Abe and have an audience with Emperor Akihito during the trip, which follows his headline-grabbing state visit to China last week.
Duterte, a self-proclaimed socialist with close links to communists, announced in Beijing the Philippines' "separation" from the United States, throwing into doubt a 70-year alliance that is anchored on a mutual defence treaty.
But his anti-American vitriol also continued.
Duterte said today he was not a "lapdog" of the United States, and again voiced anger at American and European criticism of apparent extrajudicial killings on his watch.
"You are a son of a whore," he said referring to his critics.
"Do not make us dogs. Do not. As if I am a dog with a leash and then you throw bread far away that I cannot reach."