At the outset of his statement, Mr. Trump declared, “The world is a very dangerous place!” Indeed. He is making it more so by emboldening despots in Saudi Arabia and elsewhere. The killing, revealed in all its inhuman detail by a Turkish audio recording and followed by a stream of lies revising previous lies from the Saudi regime, seemed to reflect arrogance of a rising breed of autocratic rulers impervious to shame or moral judgment. Mr. Trump is confirming them in their impunity.

In simplistic and often inaccurate terms, the statement reflected Mr. Trump’s view that all relationships are transactional, and that moral or human rights considerations must be sacrificed to a primitive understanding of American national interests — or as he put it, “America first!” “We may never know all of the facts surrounding the murder of Mr. Jamal Khashoggi,” the president declared. “In any case, our relationship is with the Kingdom of Saudi Arabia.”

Mr. Trump’s first reference to Mr. Khashoggi came only after a long riff about Iran, which Mr. Trump depicted, remarkably, as solely responsible for the war in Yemen. With disregard for the abundant evidence that Saudi Arabia has waged an indiscriminate air campaign that is responsible for a humanitarian disaster, he claimed that the Saudis would “gladly” withdraw if Iran did, and would provide humanitarian assistance. That was followed by a passage on the tens of billions of dollars in arms sales and investment Mr. Trump claims he has extracted from Saudi Arabia — claims that are vastly overblown.

When Mr. Trump did briefly note Mr. Khashoggi’s murder — “a terrible one” — the president repeated Saudi slanders that the journalist was an “enemy of the state” and an Islamist, disingenuously adding that this did not affect his thinking. It’s not the first time Mr. Trump has suggested that this is not someone for whom America should jeopardize its interests.

In the absence of leadership from the president, it falls to Congress to take action and protect America’s standing in the world. Mr. Trump knows he is on a collision course with the legislature: His statement concludes with a challenge to members of Congress who “for political or other reasons, would like to go in a different direction” to go ahead and try.