Richard Downes reports for BBC World

The decision, contained in a royal decree, means that the 36-year-old prince replaces the King's brother, Prince Hassan, who has been Crown Prince since 1965.

There had been mounting speculation about the succession following King Hussein's return from cancer treatment in the US last week.

Richard Downes in Amman: King had wanted change

The King appeared to fuel the rumours by saying he was considering change, and recalling that he had made his brother his heir because at the time, there had been no alternative.

King 'unhappy'

Prince Hassan: Had been heir since 1965

On Friday, Prince Hassan was reported to have been informed that he would be removed from the succession during an audience with the King.

The BBC correspondent in Amman, Richard Downes, says no reason has been given for Prince Hassan's removal, although it is believed King Hussein may have been unhappy with his brother's performance as regent while he was abroad.

Correspondents in Amman say that although Prince Hassan was seen as an intellectual who lacked the common touch, the abrupt manner of his removal has caused surprise.

It remains unclear what his future role will be, although reports from Amman say he may be given a special role dealing with economic affairs and the Middle East peace process.

The King - who is one of the world's longest-serving rulers - returned to Jordan earlier this week following six months of treatment.

Officials say he has been cured following six rounds of chemotherapy and a marrow cell transplant for non-Hodgkin's lymphoma.

He has been King since 1952, surviving coup attempts, wars and illness.

A military background

Prince Abdullah is Hussein's son from his second marriage, to a British woman, Toni Gardiner, who adopted the name Mona when she converted to Islam upon her marriage.

Abdullah is an army major-general and in charge of a special force which oversees the security of the royal dynasty.

He attended military schools in the UK and the United States.

The other prince who was considered a possible choice as heir is Hamza, Hussein's son from his current marriage to American-born Queen Noor, the former Elizabeth Halaby.