Trump sparked uproar earlier this year by declaring that America would take over Gaza and turn it into a "Riviera of the Middle East", prompting Arab leaders to come up with a plan to rebuild the territory at a March summit in Cairo.

Palestinian president Mahmud Abbas was the first Arab leader to arrive in Baghdad Friday.

But a diplomatic source said that most Gulf countries will attend at a ministerial level.

The war in Gaza is expected to dominate the agenda, especially after Israel approved plans to expand its offensive and spoke of the "conquest" of the territory.

United Nations chief Antonio Guterres will attend the summit, and Spanish Prime Minister Pedro Sanchez -- who has sharply criticised Israel's devastating offensive in Gaza -- is expected to address it as a guest.

Iraqi Foreign Minister Fuad Hussein said the Baghdad summit will endorse decisions that were made in Cairo's meeting in March to support Gaza's reconstruction as an alternative to Trump's widely condemned proposal.

Trump on Thursday reiterated from Qatar that he wanted the US to "take" Gaza and turn it into a "freedom zone".

- Syria, Iran -

Iraq has only recently regained a semblance of normalcy after decades of devastating conflict and turmoil, and its leaders view the summit as an opportunity to project an image of stability.

In an op-ed about the summit earlier this month, Prime Minister Mohammed Shia al-Sudani wrote: "Today, we are not just rebuilding Iraq, we are also reshaping the Middle East through a balanced foreign policy, a wise leadership, development initiatives, and strategic partnerships."

Baghdad last hosted an Arab League summit in 2012, amid domestic tensions and at the start of the war in neighbouring Syria, which only six months ago entered a new chapter after the fall of longtime ruler Bashar al-Assad.

In Riyadh, Trump met Syria's interim President Ahmed al-Sharaa, a onetime jihadist whose Islamist group spearheaded the offensive that toppled Assad.

Sharaa, who was imprisoned for years in Iraq on charges of belonging to Al-Qaeda following the 2003 US-led invasion, will miss Baghdad's summit after several powerful Iraqi politicians voiced opposition to his visit.

Foreign Minister Asaad al-Shaibani will represent Damascus instead.

The summit also comes amid Iran's ongoing nuclear talks with the United States.

Trump has pursued diplomacy with Iran as he seeks to stave off a threatened military strike by Israel on Iran -- a desire shared by many of the region's leaders.

On Thursday, Trump said a deal was "getting close", but by Friday, he was warning that "something bad is going to happen" if the Iranians do not move fast.