A new American intelligence assessment of global threats has concluded that North Korea is “unlikely to give up” all of its nuclear stockpiles, and that Iran is not “currently undertaking the key nuclear weapons-development activity” needed to make a bomb, directly contradicting two top tenets of President Trump’s foreign policy.

Daniel R. Coats, the director of national intelligence, also challenged Mr. Trump’s insistence that the Islamic State had been defeated, a key rationale for his decision to exit from Syria. The terror group, the annual “Worldwide Threat Assessment” report to Congress concluded, “still commands thousands of fighters in Iraq and Syria,” and maintain eight branches and a dozen networks around the world.