WASHINGTON — A new American intelligence assessment of global threats has concluded that North Korea is unlikely to give up its nuclear stockpiles and that Iran is not, for now, taking steps necessary to make a bomb, directly contradicting the rationale of two of President Trump’s foreign policy initiatives.

Those conclusions are part of an annual “Worldwide Threat Assessment” released on Tuesday that also stressed the growing cyberthreat from Russia and China, which it said were now “more aligned than at any point since the mid-1950s.”

The 42-page threat report found that American trade policies and “unilateralism” — central themes of Mr. Trump’s “America First” approach — have strained traditional alliances and prompted foreign partners to seek new relationships.

In testimony before the Senate Intelligence Committee linked to the release of the report, the nation’s intelligence chiefs tried to avoid directly questioning administration policies. Yet they detailed a different ranking of the threats facing the United States, starting with cyberattacks and moving on to the endurance of the Islamic State and the capabilities of both North Korea and Iran.