WASHINGTON (AFP) - The Democratic-led United States House of Representatives will vote on Thursday (Jan 9) to prevent President Donald Trump from waging war with Iran after he ordered the killing of a top general, Speaker Nancy Pelosi said.

Ms Pelosi said that the Democrats will move forward because their concerns were not addressed in a closed-door briefing to lawmakers on Wednesday by Secretary of State Mike Pompeo and other top officials.

"The president has made clear that he does not have a coherent strategy to keep the American people safe, achieve de-escalation with Iran and ensure stability in the region," she said in a statement.

"Our concerns were not addressed by the president's insufficient War Powers Act notification and by the administration's briefing today," she said.

Under the 1973 War Powers Act, the administration needs to notify Congress on major military actions, but Mr Trump, unusually, has kept classified his rationale for a strike that killed powerful Iranian general Qassem Soleimani while he was in Iraq.

Ms Pelosi said that the House would therefore vote, under the 1973 Act, to limit Mr Trump's ability to wage war against Iran.

She said that the House may also soon consider revoking the authorisation of force approved after the Sept 11, 2001 attacks on the US.

Three successive administrations have cited that authorisation as legal justification for an array of military actions across the Islamic world.

But any move to constrain Mr Trump would likely have a difficult chance of passage in the Senate, where his Republican Party holds a majority.