Some 5,000 US troops remain in Iraq, most in an advisory role.
In Baghdad, parliament voted for the government to work on a plan to end the presence of United States troops in Iraq.
Trump did not notify the so-called Gang of Eight-the top lawmakers in each chamber and the leaders of the House and Senate's Intelligence Committees-about the drone strike that killed Soleimani, a courtesy that is typically extended to Washington's leaders by a president.
Following Monday's procession, the general's remains will be taken to Qom, one of the holiest cities for Shia Islam, before being buried in his hometown of Kerman on Tuesday.Soleimani, a designer of Iran's clandestine and military operations overseas, is the first dignitary in modern history to have received a funeral ceremony in several cities across Iran. Meanwhile, Iraq's parliament voted in favour of a resolution calling for an end of the foreign military presence in their nation, an effort aimed at expelling the 5,000 USA troops stationed there over the war against the Islamic State group.
Acting Lib Dem co-leader Sir Ed Davey said Mr Johnson's "silence on Trump's unsafe assassination in Iraq is deafening". It cost billions of dollars to build.
He added: "The capabilities are there, they've been there for a long time". Speaking with reporters Sunday as he returned to Washington from his holiday stay in Florida, he doubled down, despite worldwide prohibitions. "We're not leaving unless they pay us back for it", he told reporters.
The last time the United States killed a major military leader in a foreign country was during World War II, when the American military shot down the plane carrying the Japanese admiral Isoroku Yamamoto.
"Iran's nuclear programme no longer faces any limitation in the operational field", the Iranian government said in a statement on Sunday night. "Iran rips the mask off the idea it ever fully complied with the nuclear deal, or that it made a strategic decision to forswear nuclear weapons".
While the announcement appears to signal the deal's ultimate collapse, Tehran will continue to cooperate with the United Nations nuclear watchdog, the International Atomic Energy Agency, and plans to return to full compliance to the deal's original terms once US sanctions on the economy are lifted.
Until now, Iran has said it needs to enrich uranium up to a level of 5% to produce fuel for electricity generation in nuclear power plants. Tehran has already broken some of the deal's limits as part of a step-by-step pressure campaign to get sanctions relief.
"As before, Iran will continue its cooperation with the International Atomic Energy Agency (IAEA)", according to Iran's announcement on Sunday.
"This is a temporary victory for the parties which are pro-Iranian", said the official.
"From now on, Iran's nuclear program will advance based on its own technical requirements", it said.
"In the world of politics, all developments are interconnected", Mr Mousavi said.
One US national security official said Trump's threat had caught many in the administration off guard and prompted calls for others in the government, including Pompeo, to clarify the matter.
The majority of about 180 legislators present in Parliament voted in favor of the troop-removal resolution. It was backed by most Shiite members of Parliament, who hold a majority of seats.
Sunday's parliamentary resolution was passed by overwhelmingly Shi'ite lawmakers, as the special session was boycotted by most Sunni Muslim and Kurdish lawmakers.
"Iran is unlikely to do something in the next 48 hours. but they are not forgetting about this three months from now, six months from now when we're in the general election campaign of 2020, which I think is going to put Trump in a very hard position position".
"These Media Posts will serve as notification to the United States Congress that should Iran strike any US person or target, the United States will quickly & fully strike back, & perhaps in a disproportionate manner", the president tweeted.
Iranian Foreign Minister Mohammad Javad Zarif said the killing of Soleimani was a breach of global law and that any targeting of cultural sites would constitute a war crime.
In his comments on Sunday, Prime Minister Abdel Mahdi decried the US strike as illegal and defended Soleimani, claiming that the Iranian general was his guest and that they had planned to meet on the morning he was killed to go over a Saudi proposal to defuse tensions. They're allowed to torture and maim our people.
Mohammad Javad Zarif, Iran's foreign minister, said Sunday that a red line had been crossed: "Those masquerading as diplomats and those who shamelessly sat to identify Iranian cultural & civilian targets should not even bother to open a law dictionary".
The big picture: A US withdrawal from Iraq - something Trump has long wanted but has felt forced to defer - would deeply undercut America's ability to fight ISIS.
The Iranian regime's top military official, Qassem Soleimani, was killed early on January 3 in a US airstrike near Baghdad International Airport.
The U.S. Embassy in Saudi Arabia warned Americans "of the heightened risk of missile and drone attacks".
Others in attendance criticized any support for the Iranian government as a small group of counter-protesters called Soleimani a terrorist.
Demonstrators also carried red Shi'ite flags, which traditionally both symbolise the spilled blood of someone unjustly killed and call for their deaths to be avenged. Not even Ayatollah Ruhollah Khomeini, who founded the Islamic Republic, received such an honor after his death in 1989.