RIYADH (AFP) - US President Barack Obama landed in Saudi Arabia on Tuesday to shore up ties with new King Salman and offer condolences after the death of his predecessor and half-brother, King Abdullah.

Air Force One touched down at King Khalid International Airport in the capital Riyadh, arriving from India where Obama cut short a state visit to travel to the ultra-conservative Muslim kingdom, a key US ally.

Saudi television showed King Salman welcoming Obama and his wife Michelle at the bottom of a red-carpeted ramp before a military band played the US and Saudi national anthems. A row of stars and stripes flags flew beside Saudi Arabia's green standards.

In contrast to Saudi women, required to dress head-to-toe in black, Michelle Obama wore dark slacks and a blue top with her hair uncovered.

Crown Prince Mohammed bin Nayef, the kingdom's powerful former interior minister, and Oil Minister Ali al-Naimi were among the officials welcoming the US leader, television showed.

The US president then boarded a black limousine taking him to talks with King Salman at a palace in the city centre. The four-hour stopover was also to include a dinner before the US delegation continues on to Germany.

King Salman, 79, acceded to the throne after King Abdullah died on Friday aged about 90. Authorities deployed armoured vehicles, police cars and radar all along the route into the city from the airport to secure Obama's visit, an AFP reporter observed. A row of stars and stripes flags flew beside Saudi Arabia's green standards.

Despite the longstanding partnership, analysts say Riyadh has grown dissatisfied with what it sees as a lack of US engagement with regional crises as Washington looks to Asia. Anwar Eshki, chairman of the Jeddah-based Centre for Strategic and Legal Studies, said "divergences persist".

The differences include the battle against the Islamic State in Iraq and Syria (ISIS), the nearly four-year-old rebellion against the Damascus regime and the post-Arab Spring chaos in Libya and Yemen.

Salman Shaikh, director of the Brookings Doha Centre, said the US-Saudi relationship "is not what it was". Ties were better under both George Bush and his son George W. Bush, who had a "relationship that was very much built on personal foundations," said Shaikh.

The late king had a strained personal relationship with Obama, said Frederic Wehrey, of the US-based Carnegie Endowment for International Peace Middle East Programme.

Among the 29 members of Obama's delegation are former Bush-era officials including James Baker, secretary of state during the first Gulf War against Iraqi dictator Saddam Hussein, former national security adviser Brent Scowcroft, and Condoleezza Rice, who served as secretary of state under George W. Bush.

ISIS, YEMEN ON AGENDA

Central Intelligence Agency director John Brennan and General Lloyd J. Austin III, head of US Central Command, also accompanied Obama. They had all been with him in India but Secretary of State John Kerry and Senator John McCain joined the president especially for his Saudi trip.

"We wanted to make sure that we had bipartisan representation given the deep congressional interest in Saudi Arabia," Deputy National Security Adviser Ben Rhodes said. McCain, a Republican, chairs the Senate Armed Services Committee, and had been in Saudi Arabia as part of a Middle East tour several days ago. During that trip he called for "additional US boots on the ground in Iraq and Syria" to defeat ISIS.

Rhodes confirmed in New Delhi that the turmoil in Yemen and the battle against ISIS would figure among "leading issues" on the Riyadh agenda. "Clearly that would include the continued counter-ISIL campaign where the Saudis have been a partner and have joined us in military operations," he said, using an alternative acronym for ISIS. "That of course also includes the situation in Yemen where we have coordinated very closely with Saudi Arabia and the other countries."

The Saudi royal court said King Salman would hold talks with Obama on "regional and international issues of common interest, in addition to means of enhancing bilateral relations."

Obama is the latest, and the most powerful, leader to converge on Riyadh since Friday. His welcome was the most elaborate but sheikhs, presidents and prime ministers from Europe, Asia, Africa and the Americas, all came to pay their respects. Singapore was represented by Deputy Prime Minister Teo Chee Hean.

It is a recognition of the kingdom's power as the world's leading oil exporter, a political heavyweight in a region threatened by extremist violence, and as home to Islam's holiest sites.