Kuwait's Crown Prince Mishal Al Ahmad Al Jaber Al Sabah has arrived in Amman to attend the royal wedding, Jordanian state TV said on Thursday.
The UK's Prince William and his wife Catherine have also arrived.
Their attendance was only confirmed by Jordanian state media a few hours before the start of the palace ceremony.
Malaysia's king and US first lady Jill Biden have arrived in Jordan for the wedding of Crown Prince Hussein, the first of dozens of international guests expected for Thursday's event.
The Crown Prince will wed Rajwa Al Saif, a Saudi national whose mother is related to King Salman. Saudi Crown Prince Mohammed bin Salman is widely expected to be among the most senior Arab figures attending the wedding.
The wedding is set to promote Jordan's image as bastion of stability in the Arab Levant. The country has been ruled by the Hashemite monarchy since it was founded as a British protectorate in 2021.
No official list of attendees has been released.
The official Jordanian news agency said King Abdullah met on Wednesday with King Al Sultan Abdullah of Malaysia. Mrs Biden arrived by plane in Amman on Wednesday.
King Abdullah held a dinner on Wednesday for several thousand Jordanians, mainly attended by present and former officials and members of tribes who form the bedrock of support for the political system.
The National's Mahmoud Rida reports from Amman ahead of royal wedding
"Our joy is complete with your presence," the king told the dinner party, which mostly comprised present and former officials, as well as tribal figures and members of the security forces.
The authorities have declared a holiday on Thursday. Roads through which the bride and groom will be driven have been decorated with Jordanian flags and pictures of the Crown Prince.
Maj Gen Yousef Huneiti, Jordan's chief of staff, said special military units have been deployed for the event.
Among them are the Royal Guards, who will protect the couple as they travel in a convoy from Zahran Palace in west Amman, where they will sign the wedding papers, to another palace on the outskirts of the city, where a reception will be held.
Their wedding car will be accompanied through the streets of the capital by red 1980s roofless Land Rovers and red BMW motorcycles belonging to the guards.
The guards trace their origin to an infantry battalion established under the late King Abdullah I, Jordan's first monarch, who ruled from 1921 to 1951.
The Sheikh Mohamed Bin Zayed Al Nahyan Brigade, a Jordanian rapid intervention unit named after President Sheikh Mohamed, has also been deployed, Maj Gen Huneiti said.
