(WashingtonPost) -- The information the president relayed had been provided by a U.S. partner through an intelligence-sharing arrangement considered so sensitive that details have been withheld from allies and tightly restricted even within the U.S. government, officials said.

The partner had not given the United States permission to share the material with Russia, and officials said Trump’s decision to do so endangers cooperation from an ally that has access to the inner workings of ISIS. After Trump’s meeting, senior White House officials took steps to contain the damage, placing calls to the CIA and the National Security Agency.

“This is code-word information,” said a U.S. official familiar with the matter, using terminology that refers to one of the highest classification levels used by American spy agencies. Trump “revealed more information to the Russian ambassador than we have shared with our own allies.”

The revelation comes as the president faces rising legal and political pressure on multiple Russia-related fronts. Last week, he fired FBI Director James B. Comey in the midst of a bureau investigation into possible links between the Trump campaign and Moscow. Trump’s subsequent admission that his decision was driven by “this Russia thing” was seen by critics as attempted obstruction of justice.

One day after dismissing Comey, Trump welcomed Russian Foreign Minister Sergei Lavrov and Ambassador Sergey Kislyak — a key figure in earlier Russia controversies — into the Oval Office. It was during that meeting, officials said, that Trump went off script and began describing details of an ISIS terrorist threat related to the use of laptop computers on aircraft.