U.S. security chiefs visited Saudi Arabia on Wednesday to convey President Barack Obama's condolences for the death of Crown Prince Nayef, underscoring the importance of a relationship seen as key in the battle against al Qaeda.

The delegation was led by Defense Secretary Leon Panetta and included Federal Bureau of Investigation director Robert Mueller, Assistant to the President for Homeland Security, Counter-terrorism John Brennan and former Central Intelligence Agency director George Tenet.

Mike Morrell, the CIA's deputy director, also joined the delegation which met Prince Salman, the new crown prince.

"The president wanted me ... to convey to you not only our sorrow for your loss but also our best wishes to you in your new position," Panetta told Prince Salman at the Royal Court in Jeddah, where delegations from around the world were visiting.

Nayef, who was interior minister for 37 years, built up a formidable domestic security apparatus which crushed al Qaeda inside the kingdom and has helped foil attempts by the militant group to attack international targets from its base in Yemen.

"He played a pivotal role in strengthening the relationship between the United States and the kingdom of Saudi Arabia," Panetta said in a statement late on Tuesday.

After the September 11, 2001, attacks on the United States, Prince Nayef was at first unwilling to accept that Saudi citizens could have participated, when they in fact made up 15 of the 19 hijackers.

But former diplomats to the kingdom said he later reversed this position and worked closely with U.S. security forces after a string of al Qaeda attacks hit targets inside Saudi Arabia.

King Abdullah on Monday named Prince Salman, defense minister in the world's top oil exporter, as his new heir.

Salman is responsible for Saudi Arabia's multi-billion dollar arms purchases which have historically been used to cement relations with key allies including Washington.

However, analysts say Nayef's death will likely not affect the kingdom's security operations as his long-time deputy Prince Ahmed was appointed to replace him as interior minister.

Nayef's son Prince Mohammed bin Nayef has stayed on as head of the security forces which have been praised by U.S. officials for expelling al Qaeda from Saudi Arabia.

"Prince Nayef was involved in strategic decisions, not the day-to-day operational side, so I don't think we will see any change, particularly on counter terrorism," said Mustafa Alani, a security expert at the Gulf Research Centre based in Jeddah.

"Prince Ahmed will endorse the operational policy of Prince Mohammed and continue the close relationship with the U.S., not only inside Saudi but on Yemen, Somalia ... It's region-wide," Alani added.

After stepping off the plane, Panetta, in a dark suit, shook hands and smiled as he was greeted by the Saudi protocol chief.

British Defense Secretary Philip Hammond and Prince Andrew the Duke of York offered condolences to Crown Prince Salman on Tuesday.