WASHINGTON (AP) - The Trump administration has plunged into a showdown with Congress over access to a whistleblower's reported complaint about incidents including a private conversation between President Donald Trump and a foreign leader.

The government's intelligence watchdog says the blocked complaint is "serious" and "urgent." The administration is keeping Congress from even learning what exactly the whistleblower is alleging, but the intelligence community's inspector general says the matter involves the "most significant" responsibilities of intelligence leadership.

One report said it involved a promise Trump made in a phone call to a foreign leader. A lawmaker said the complaint was "based on a series of events."

The inspector general appeared before the House intelligence committee behind closed doors Thursday but declined, under administration orders, to reveal the substance of the complaint.