The Emir of Qatar named his fourth son as heir apparent yesterday, replacing an older son as crown prince.

His Highness Sheikh Hamad bin Khalifa Al Thani had accepted a decision by Sheikh Jassim bin Hamad bin Khalifa Al Thani to quit as crown prince, according to a royal decree carried by the news agency QNA.

Younger brother Sheikh Tamim bin Hamad bin Khalifa Al Thani will replace him in the role. Both sons are in their 20s.

QNA said Sheikh Jassim sent a letter to his father explaining his decision to quit, saying "the time is appropriate to step down and prepare for a successor".

The letter, carried by the agency, did not give specific reasons but Sheikh Jassim said he had "reluctantly" accepted the post in 1996.

Sheikh Jassim is Sheikh Hamad's third son. Sheikh Tamim, who heads the Olympic committee, is his fourth. The Emir in the decree appreciated his elder son for the work he had done while in office and said the younger son has been appointed as his noble qualities had qualified him for the post.

The Emir's eldest son is a businessman and his second is involved in Islamic charities. Neither has shown any interest in becoming crown prince.

In a televised ceremony, Sheik Hamad accepted his son's resignation. The ceremony was attended by royal family members, including Prince Tamim, and senior Qatari officials.

In the letter to his father, Prince Jassim said he had initially accepted the position in October 1996 because of "sensitive circumstances."

"Although I have never and will never slack in serving my country under your leadership, I did not want, as I have told you from the start, to be appointed as crown prince," Prince Jassim wrote.

In his responding letter, Sheik Hamad said he had repeatedly tried to change his son's mind. "With all my appreciation to you, dear son, I have nothing to do ... but to accept with great regret your decision in spite of the sorrow and pain I feel," he said.