Saudi activists have urged women to defy a traditional driving ban and get behind the wheel on Saturday, the second day of a visit by U.S. President Barack Obama.

"We have fixed a day every month to pursue our campaign," activist Madiha al-Ajroush told Agence France Presse Friday, insisting that it was a coincidence their latest protest and Obama's visit came on the same day.

U.S. President Barack Obama sought Friday to allay Riyadh's criticism of his policies on Syria and Iran, telling the Saudi king their two countries remain in lockstep on strategic interests.

He also assured King Abdullah that the U.S. "won't accept a bad deal" with Iran, as global powers negotiate a treaty reining in Tehran's controversial nuclear program.

Prince Moqren bin Abdul Aziz, named second in line for the Saudi throne, is a confidant of King Abdullah who has trusted him to carry out several sensitive diplomatic missions.

Born on September 15, 1945 in Riyadh, the second crown prince is the youngest of the 35 sons of Abdul Aziz bin Saud, the founder of the kingdom.

Saudi King Abdullah's unprecedented decision to appoint a second heir to his throne appears aimed at ensuring a smooth succession in a region thrown into turmoil by the Arab Spring.

It also opens the door for the next generation to step up, in an ultra-conservative state ruled for decades by aging monarchs.

Saudi Arabia's 90-year-old King Abdullah on Thursday appointed his half-brother Moqren, 69, as the next heir to the throne of the world's largest exporter of crude oil.`

The decision, announced in a royal decree, comes as a source close to the circle of power told Agence France Presse that current Crown Prince Salman, 79, was sick and "may decide not to claim the throne" because of his ill health.

A former wife of Saudi Arabia's King Abdullah appealed to U.S. President Barack Obama on Thursday for help in the case of four daughters she says are being held in a royal palace.

Alanoud AlFayez, 57, a Jordanian national who has lived in London since her divorce from the Saudi monarch in 2003, said her children needed to be "saved".

Dozens of U.S. lawmakers have urged President Barack Obama to publicly address Saudi Arabia's "systematic human rights violations" when he visits the kingdom Friday.

With their decades-old alliance fraying amid tensions over Washington's efforts to reach a nuclear deal with Iran and its reluctance to engage more forcefully in Syria, regional issues are expected to take precedence when Obama meets with King Abdullah on the U.S. leader's second visit to Riyadh since taking office in 2009.

The White House said Tuesday it is "very disappointed" that Saudi Arabia has denied a Jerusalem Post reporter's visa to cover President Barack Obama's visit to the kingdom later this week.

Deputy national security adviser Ben Rhodes said the White House made clear to the Saudis the importance that the reporter have access to cover the trip.

Jakarta called Monday for a Saudi family to accept a substantial payment and halt the impending execution of an Indonesian maid on death row in the kingdom for murder.

If the execution of Satinah Binti Jumadi Ahmad goes ahead, it could set back attempts by Indonesia and Saudi Arabia to mend ties damaged by the 2011 beheading of an Indonesian maid, who was also guilty of murder.

A Saudi man convicted of shooting dead a compatriot in a dispute was beheaded by the sword on Monday, the interior ministry said.

Mohammed bin Khamees al-Hantushi al-Enzi was found guilty of killing Ibrahim bin Marfu al-Enzi, the ministry said in a statement carried by the SPA state news agency.