Washington (CNN) The Trump administration will brief House and Senate lawmakers behind closed doors on Wednesday about the killing of Iranian commander Qassem Soleimani, four sources familiar with the plans told CNN.

Secretary of State Mike Pompeo, Defense Secretary Mark Esper, Chairman of the Joint Chiefs Mark Milley and CIA Director Gina Haspel are expected to brief senators, the sources said. It is unclear if the same officials will also speak with House lawmakers.

News of the briefing comes as lawmakers continue to question the administration's motives for conducting the strike and challenge its shifting explanations as to why it was legally justified.

Senate Minority Leader Chuck Schumer and Sen. Bob Menendez, the top Democrat on the Senate Foreign Relations Committee, sent a letter to President Donald Trump Monday calling on him to declassify the formal notification given to Congress regarding the US drone strike that killed Soleimani.

"It is critical that national security matters of such import be shared with the American people in a timely manner," says the letter. "An entirely classified notification is simply not appropriate in a democratic society, and there appears to be no legitimate justification for classifying this notification."

Read More