The Iraqi parliament passed a resolution Sunday calling on the government to expel U.S. troops from the country in response to the killing of Iranian Gen. Qasem Soleimani and the leader of an Iraqi militia on its soil.

Between the lines: A senior Iraqi government official told Axios' Jonathan Swan that the actual expulsion of U.S. troops is far from a certain outcome. This is a resolution and the prime minister who must sign it has already resigned, the official said.

"This is a temporary victory for the parties which are pro-Iranian," they added. "But it's also a clear message from the Sunnis and from the Kurds [who didn't vote] and from some Iraqi Shia for the Americans to tell them we want you to stay in Iraq."

The big picture: The legal basis for the U.S. presence in Iraq is that it comes at Iraq's invitation. This vote does not formally revoke that invitation, but it is a step along that path. A U.S. exit from Iraq could ultimately be one of the most consequential results of Soleimani's killing, because it would significantly hamper the fight against ISIS and achieve a major Iranian objective.

What they're saying: Iraqi Prime Minister Adel Abdul-Mahdi said Iraq "cannot accept" a "political assassination" on its soil. He called the attack a grave violation of Iraqi sovereignty.

Mahdi also revealed that Soleimani was in Baghdad at the time of his killing to meet with him and relay Iran's response to a Saudi request for dialogue.

Mahdi noted that he had personally worked to defuse the protests outside the U.S. Embassy in Baghdad earlier in the week, going so far as to threaten to step down if the militia behind the protests did not disperse.

President Trump thanked him for that effort, he said, at the same time he was planning an attack inside Iraq without permission.

Mahdi, who resigned in November amid mass protests in Iraq but remains as caretaker prime minister, previously warned that President Trump's decision would "light the fuse of war."

State Department spokesperson Morgan Ortagus said in a statement Sunday afternoon:

" The United States is disappointed by the action taken today in the Iraqi Council of Representatives. While we await further clarification on the legal nature and impact of today’s resolution, we strongly urge Iraqi leaders to reconsider the importance of the ongoing economic and security relationship between the two countries and the continued presence of the Global Coalition to Defeat ISIS. We believe it is in the shared interests of the United States and Iraq to continue fighting ISIS together. This administration remains committed to a sovereign, stable, and prosperous Iraq."

Behind the scenes: U.S. military leaders were "stunned" that Trump gave the order to kill Soleimani, a step they viewed as the "most extreme response to recent Iranian-led violence in Iraq," per the NY Times.

Trump administration officials have since said Trump had little choice because Soleimani was planning imminent attacks on U.S. and allied forces in the region, but they have presented no evidence of such plans.

The resolution passed today calls not only on U.S. troops to leave Iraq, but the entire international coalition fighting the Islamic State.

Go deeper: Anti-ISIS coalition suspends operations due to Iran threat