The whistleblower complaint that has triggered a tense showdown between the U.S. intelligence community and Congress involves President Trump’s communications with a foreign leader, according to two former U.S. officials familiar with the matter.

Trump’s interaction with the foreign leader included a “promise” that was regarded as so troubling that it prompted an official in the U.S. intelligence community to file a formal whistleblower complaint with the inspector general for the intelligence community, said the former officials, speaking on the condition of anonymity because they were not authorized to discuss the matter publicly.

It was not immediately clear which foreign leader Trump was speaking with or what he pledged to deliver, but his direct involvement in the matter has not been previously disclosed. It raises new questions about the president’s handling of sensitive information and may further strain his relationship with U.S. spy agencies. One former official said the communication was a phone call…

Intelligence Community Inspector General Michael Atkinson determined that the complaint was credible and troubling enough to be considered a matter of “urgent concern,” a legal threshold that ordinarily requires notification of congressional oversight committees.