US President Donald Trump has welcomed Iraq's new Prime Minister Ali al-Zaidi to the White House after strongly backing the political neophyte in his bid for office.

The issue of Iran is likely to loom large in the discussions on Tuesday.

Iraq has been under pressure to disarm a network of what US says are Iran-backed militias operating in the country, some of which launched attacks on US bases and diplomatic facilities after the US and Israel launched their war against Iran in February.

Officially, the Iraqi government has given non-state armed groups until the end of September to disarm, but some of the most powerful militias have said they have no intention of doing so.

A Trump administration official said ahead of the Oval Office meeting that the US will make "informed" decisions based on Iraq’s efforts to disarm militias inside its borders. The official was granted anonymity to discuss the administration’s strategy ahead of al-Zaidi’s visit.

Al-Zaidi, a businessman with no political background, emerged as a consensus candidate in Iraq after months of deadlock over the premiership following last year’s parliamentary elections.

When al-Zaidi was formally chosen as prime minister-designate in April, Trump said in a social media post that it was the "beginning of a tremendous new chapter between our Nations — Prosperity, Stability, and Success like never seen before."

But Trump’s interest and involvement in the next leadership in Iraq began long before that statement.

Crack down on corruption

Iraq’s dominant parliamentary bloc, the Coordination Framework — a coalition of Shia parties allied with Iran — initially said it would back former Prime Minister Nouri al-Maliki, whom the Trump administration views as too close to Tehran.

The US president publicly announced his opposition to al-Maliki and threatened to cut off aid to Iraq if he was appointed, adding that "if we are there to help, Iraq has ZERO chance of Success, Prosperity, or Freedom."

Since taking office, al-Zaidi has made a public show of cracking down on corruption.

His government has conducted raids and arrested dozens of current and former lawmakers and government officials accused of corruption, including a number affiliated with former Prime Minister Mohammed Shia al-Sudani.

The Iraqi premier’s delegation to Washington includes a number of Iraqi businessmen as well as government officials, and al-Zaidi’s office said in a statement that the aim of the visit is to "strengthen economic and development partnerships, attract investment, and expand the role of US companies in implementing infrastructure projects" and to further develop the oil-rich country’s energy sector.

Outlining his vision for a new US-Iraq partnership, PM al-Zaid wrote an op-ed in The Washington Post last week, stressing: "My government is disarming militias, strengthening the rule of law and opening the country to American investment."

"Iraqis have endured war, dictatorship and terrorism. Today, they understand that the time has come to write a new chapter in Iraq’s relationship with the world and with its strategic partners, one founded on integration into the global economic and financial system," he said.

"I carry to the United States a message of confidence: that a sovereign Iraq stands apart from regional alignments and conflicts, and chooses instead the path of development, with an open hand extended to its friends."

PM al-Zaidi is expected to remain in the US for one week.