US president Donald Trump threatened sanctions against Iraq and said that if US troops were required to leave the country, Iraq's government would have to pay Washington for the cost of a "very extraordinarily expensive" air base there.
He said if Iraq asked US forces to leave on an unfriendly basis, "we will charge them sanctions like they've never seen before ever. It'll make Iranian sanctions look somewhat tame."
The Iraqi parliament passed a resolution calling for an end to all foreign troop presence, reflecting the fears of many in Iraq that Friday's strike could engulf them in another war between two bigger powers long at odds in Iraq and across the region.
While such resolutions are not binding on the government, this one is likely to be heeded: Prime Minister Adel Abdul Mahdi had earlier called on parliament to end foreign troop presence as soon as possible.
Iran and the United States have been competing for clout in Iraq since the US-led invasion in 2003 that toppled dictator Saddam Hussein.
VOTE ON FOREIGN TROOPS
Before Trump's comments to reporters, a State Department spokeswoman said the United States was waiting for clarification of the legal nature and impact of the resolution, and strongly urged Iraqi leaders to reconsider the importance of the two nations' ongoing economic and security relationship.
Some 5,000 US troops remain in Iraq, most in an advisory role.
Abdul Mahdi said that despite the "internal and external difficulties" the country might face, canceling its request for help from US-led coalition military forces "remains best for Iraq on principle and practically."
He said he had been scheduled to meet Soleimani the day he was killed, and that the general had been due to deliver an Iranian response to a message from Saudi Arabia that Abdul Mahdi had earlier passed to Tehran. Sunni Muslim Saudi Arabia and Shi'ite Iran had been about to "reach a breakthrough over the situation in Iraq and the region", Abdul Mahdi said.
Despite decades of US-Iran enmity, Iranian-backed militia and US troops fought side by side during Iraq's 2014-17 war against Islamic State, their common enemy. Iraqi militia leader Abu Mahdi al-Muhandis was also killed in Friday's strike.
Sunday's parliamentary resolution was passed by overwhelmingly Shi'ite lawmakers, as the special session was boycotted by most Sunni Muslim and Kurdish lawmakers.
One Sunni member of parliament told Reuters both groups feared that kicking out US-led forces would leave Iraq vulnerable to insurgents, undermine security and heighten the power of Iranian-backed Shi'ite militias.
The 'E3' group of countries comprising France, Britain and Germany called on Iran to refrain from any violent action and urged it to go back to respecting arrangements laid out in the 2015 nuclear deal with world powers.
The three nations also reaffirmed their determination to fight Islamic State and called on Iraqi authorities to continue to give the necessary support to the coalition.
It was Trump's withdrawal of the United States from the deal in 2018 and reimposition of sanctions on Iran that touched off a new spiral of tensions after a brief thaw following the accord.
On Sunday, Iran further distanced itself from the agreement, saying it would continue to cooperate with the UN nuclear watchdog but would respect no limits to its uranium enrichment work.
That meant "there will be no limitations in enrichment capacity, level of enrichment and research and development and ... it will be based on Iran's technical needs," state TV said, quoting a government statement. It said the rollback of its nuclear commitments could be reversed if Washington lifted sanctions on Tehran.
As head of the Revolutionary Guards' Quds Force, Soleimani masterminded Iran's clandestine and military operations abroad, creating an arc of Shi'ite power with the help of proxy militias confronting the regional might of the United States, Israel and Saudi Arabia.
Hundreds of thousands of mourners, many chanting, beating their chests and wailing in grief, turned out across Iran to show their respects after his body was returned to a hero's welcome.