Secretary of State Mike Pompeo on Sunday defended President Donald Trump's decision to kill Iranian military commander Qassem Soleimani, as Democratic lawmakers questioned whether the action was justified and the United States braced for retaliation.

Democrats in Congress said it was not clear why the Iranian military leader, long seen as a threat by U.S. authorities, had to be killed now. They said Trump does not have the authority to go to war without congressional approval, and that his actions put the country at greater risk.

Trump's fellow Republicans in Congress have generally backed his decision.