RIYADH, Saudi Arabia – Hundreds of tribal chiefs, Islamic clerics, princes, and commoners pledged loyalty yesterday to Saudi Arabia’s new King Abdullah, vowing to “hear and obey” in a traditional Islamic ceremony that seals his status as monarch after a decade as de facto ruler.

King Abdullah’s investiture strengthens his hand to push forward with what have been the hallmarks of his unofficial rule – limited steps toward reform and a crackdown on Islamic extremism and militants linked to Al Qaeda.

“I promise God and you that I will adopt the Koran as the constitution and Islam as the course, and that all my concerns will be to establish righteousness and justice,” King Abdullah said in his first address to the nation as king. “I appeal to you to support me and help me carry this trust and don’t hesitate to advise me.”

Western dignitaries flowed through a Riyadh palace to congratulate the 81-year-old King Abdullah and express condolences for the death of his predecessor and half brother, King Fahd. King Abdullah, in white robes and a cream-colored cloak, sat with Britain’s Prince Charles and Prime Minister Blair as well as the king of Sweden and other European heads of state.

One key meeting will be with Vice President Cheney, who was to leave Washington yesterday evening for Riyadh and return early Friday.

Saudi Arabia is a major American ally in the Middle East, and King Abdullah has worked to repair ties strained by the September 11, 2001, attacks, in which 15 of the attackers were Saudis.

Foreign Minister Saud al-Faisal said he expected American-Saudi relations to continue to improve and vowed a “total war” on terrorism.

The allegiance ceremony – known as “bayah” – is key for King Abdullah, who has been de facto ruler since Fahd suffered a debilitating stroke in 1995. Fahd died Monday at age 84.

King Abdullah is believed to have met some resistance on both reform and the fight against militants from hard-liners in the Islamic clergy and their allies in the royal family, though such squabbles are kept strictly behind the scenes.

So far, reform steps have been severely limited, centered on the kingdom’s first election, held this year to pick local councils. But King Abdullah faces pressure to allow a wider number of Saudis a say in government.

Being monarch will likely boost King Abdullah in pushing through his plans. He may also be helped by money: The kingdom’s coffers are overflowing with oil profits amid rising prices – spiking to $61 on news of Fahd’s death. After years of deficits due to low oil prices, King Abdullah now has cash to please disgruntled members of the royal family.

The kingdom’s grand mufti and other top Islamic clerics were the first to file by King Abdullah, shake his hand, and vow their loyalty to him as Saudi Arabia’s sixth king.

The House of Saud has depended for legitimacy on the support of clerics from the kingdom’s strict Wahhabi version of Islam since King Abdullah’s father, Abdul-Aziz bin Saud, welded the Arabian peninsula tribes into a nation under his name in 1932.

Hundreds of tribal chiefs, royal family members, government officials, and uniformed senior military officers – all men – lined up, some shouting “Long live the king” as they waited their turn to honor King Abdullah. A palace servant swung an incense burner among them to bless the gathering, in a large marble-columned hall covered with silk carpets and graced by giant chandeliers.

Each man shook King Abdullah’s hand and pronounced, “I express my allegiance to you. I hear and obey, except in what would disobey God.”

The “bayah” ceremony has its roots in the succession after the death of Islam’s prophet Mohammed in the 7th century, when the caliphs who followed him received the support of the Muslim community.

Security was tight, with armed agents wandering the hall, wearing traditional white robes and red headdresses, toting automatic weapons and loops of ammunition.

In theory, the ceremony was open to all citizens, but security forces closed off the neighborhood surrounding the palace, set up checkpoints, and filtered those who wanted to come in. They checked ID cards, letting in those who were important and turning away others. Two helicopters hovered over the building.

Some well-wishers pushed and shoved for a place in line or pleaded with guards to let them past. Others waited outside in the blazing sun and 130-degree temperatures.

“Look what God wills, the king really has some stamina,” a 35-year-old high school gym teacher, Fahd Nasser al-Harashi, said, sweating in the heat. “God give him health. I don’t know how he can greet so many people. It really shows he’s strong and capable of leading the country.”