Secretary of State Mike Pompeo declined an invitation to appear before the House Foreign Affairs Committee to field questions regarding U.S. hostilities with Iran, a decision that has left the panel’s chairman “disappointed and frustrated,” he said Monday.

In a statement, Rep. Eliot L. Engel (D-N.Y.) said that “each passing day raises new questions” about the Jan. 3 drone strike that killed Iranian Maj. Gen. Qasem Soleimani.

“Was there really an imminent threat?” Engel said. “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 announcement of Pompeo’s decision comes after senior administration officials appeared Sunday on public affairs shows. The officials declined to confirm President Trump’s assertion that four U.S. embassies had been targeted for attack by Iran and said that Trump’s “interpretation” of the threat was consistent with overall intelligence that justified the killing of a senior Iranian general.

The administration has offered few details and differing justifications for the drone strike that killed Soleimani, ranging from retaliation for two decades of attacks on U.S. troops and allies by the Quds Force he led, to the possibility of future actions against the United States, to Trump’s claim that intelligence had confirmed imminent plans to bomb four American embassies.

In a tweet on Monday, Trump sought to deflect questions about the operation.

“The Fake News Media and their Democrat Partners are working hard to determine whether or not the future attack by terrorist Soleimani was ‘imminent’ or not, & was my team in agreement,” he tweeted. “The answer to both is a strong YES., but it doesn’t really matter because of his horrible past!”

Karen DeYoung contributed to this report.