House Foreign Affairs Committee Chairman Eliot Engel (D-N.Y.) said he is "disappointed and frustrated" that Secretary of State Mike Pompeo will not appear before the committee on Tuesday to answer questions about the U.S.-led airstrike that killed Iranian Quds Force Gen. Qassem Soleimani and resulted in increased hostility between Iran and the U.S.

Engel extended the invitation to Pompeo after Democratic lawmakers decried that President Trump did not seek Congressional approval before carrying out the Jan. 2 attack. Pompeo has repeatedly defended the surprise attack in Baghdad against Soleimani, saying it was necessary because of an imminent threat to the U.S., although neither the administration nor Pompeo has been able to explicitly define what that imminent threat was.

"Each passing day raises new questions about the strike that killed General Soleimani," Engel said in a statement Monday. "Was there really an imminent threat? Was it part of a larger operation? What was the legal justification? What is the path forward? With the wildly muddled explanations coming from the administration, the Secretary should welcome the opportunity to make the case and answer questions before the American people. The committee expects to hear from him soon.”

Pompeo has repeatedly said that Soleimani was planning an attack on U.S. diplomats and service members in the weeks leading up to his death and that information presented by top U.S. intelligence officials made it necessary for the U.S. to kill Soleimani.

Trump doubled down on the calls for further explanation of the reason behind the attack, telling Fox News' Laura Ingraham in an interview on "The Ingraham Angle" that the embassy in Baghdad was among four potential embassies being targeted by Soleimani.

Statements by Defense Secretary Mark Esper contradicted those claims when he told reporters on Sunday that he hadn’t seen hard evidence that four American embassies were under possible threat.

The House of Representatives on Thursday voted in favor of a War Powers Resolution meant to limit Trump's military action toward Iran and prevent further escalations in tensions between Washington and Tehran.

The top Iranian military leader's death triggered a series of events including threats from Iranian Supreme Leader Ayatollah Ali Khamenei and President Hassan Rouhani who vowed revenge, and a retaliatory strike by Iran on two U.S. military bases in Iraq, for which Trump has levied additional sanctions.