US President Donald Trump's son-in-law Jared Kushner met Morocco's King Mohammed VI on Tuesday in Rabat as part of a fresh push on a long-promised but yet-to-be-delivered peace plan for the region.

The trip — which will also include stops in Amman and Jerusalem — comes amid a flurry of other administration moves to shore up alliances with Arab allies against Iran and the deployment of warships and bombers to the region.

Kushner is accompanied by Jason Greenblatt, Trump's special representative for international negotiations, and Brian Hook, the special US representative for Iran.

The meeting in Rabat focused on developments in the Middle East and North Africa as well as strengthening the partnership between Morocco and the US, a palace spokesman told AFP.

Greenblatt tweeted that he and Kushner shared an iftar dinner — the traditional meal to break the daily fast during the holy month of Ramazan — with Morocco's king, Crown Prince Moulay Hassan and Foreign Minister Nasser Bourita.

"Thank you to His Majesty for a special evening and for sharing your wisdom," Greenblatt wrote. "Morocco is an important friend and ally of the United States."

The Trump administration is expected to unveil the peace plan — after numerous failures by its predecessors — possibly as early as next month, but the Palestinians have already rejected it as heavily biased in favor of Israel.

Washington has yet to commit to an exact timetable with respect to the political aspects of the plan.

Kushner is the chief architect of the proposals and Greenblatt, a longtime Trump lawyer, has served as his right-hand man on the Middle East initiative.

Upon his arrival in the White House more than two years ago, Trump proclaimed his ambition to secure a final accord ending the Israeli-Palestinian conflict. But the odds of his succeeding where every previous US president — Republicans as well as Democrats — have failed appear particularly low.

Palestinians have boycotted the process since Trump recognised Jerusalem as the capital of Israel in December 2017.

Bahrain conference

The US is expected to roll out the economic aspects of the peace plan at a conference in Bahrain on June 25 and 26.

Co-hosts the US and Bahrain have billed it as "a pivotal opportunity... to share ideas, discuss strategies and galvanise support for potential economic investments and initiatives that could be made possible by a peace agreement." But Palestinian political leaders say they will boycott it and Palestinian business leaders said they won't go either, raising further questions about the plan's viability.

"Any economic project without a political solution is selling an illusion," said Arafat Asfour, chairman of the Palestine Trade Center.

Among those declining an invitation was Bashar al-Masri, a high-profile Palestinian businessman who worked with international partners and in cooperation with the Israelis to invest $1.4 billion in the new Palestinian town of Rawabi.

Kushner, who will join up with Trump in London after his Middle East trip, has been evasive about the US plan, which has been shrouded in secrecy. While promising new ideas to revive a moribund peace process, he has refused to talk about a two-state solution, the formula that has long been at the heart of international efforts to achieve peace and also the official US position.

Instead, he has looked to an alliance with the Saudis against Iran as a way to gain Arab support for his plan.

Three days before Kushner's trip, Trump authorised $8.1 billion in arms sales to Saudi Arabia and other Arab allies, bypassing Congress.

Arms sales to the kingdom were frozen after the assassination of Saudi dissident Jamal Khashoggi in October and in response to mounting concerns over the human toll of a Saudi-led armed campaign in Yemen.

But the administration defended the sales as necessary "to deter Iranian aggression and build partner self-defense capacity".