(Reuters) - U.S. Secretary of State Anthony Blinken is in Saudi Arabia for a much anticipated visit amid frayed ties due to deepening disagreements on everything from Iran policy to regional security issues, oil prices and human rights.
The U.S.-Saudi alliance has weathered many storms over the decades, but the relationship remains vital to both: Saudi Arabia is the world's biggest oil exporter and the United States' largest foreign military sales customer.
Here are some milestones in ties:
The United States recognises the Kingdom of Hejaz and Nejd, renamed Saudi Arabia the following year.
Saudi Arabia grants an oil exploration concession to Standard Oil of California. Its Saudi branch, later renamed Aramco, makes the first commercial find in 1938.
President Franklin D. Roosevelt meets King Abdulaziz aboard the USS Quincy in the Suez Canal, setting the stage for decades of close ties.
Saudi Arabia renegotiates the Aramco concession, securing more revenue.
Saudi Arabia and the United States conclude a Mutual Defense Assistance Agreement, opening the way for U.S. arms sales.
Saudi Arabia joins an Arab oil embargo against the United States and other countries over their support for Israel in a 1973 war with Egypt and Syria. Oil prices had nearly quadrupled by the time the embargo was lifted in 1974.
With U.S. and Pakistani cooperation, Saudi Arabia helps fund Afghan resistance to Soviet occupation. Many Saudis, including Saudi-born Osama bin Laden, fund and join Afghan fighters.
Saudi Arabia completes purchase of 100% of Aramco shares.
Iraq invades Kuwait. The following year, U.S.-led forces use Saudi Arabia as a launchpad to expel Iraqi forces. Most U.S. troops then leave Saudi Arabia, but thousands remain.
A truck bomb kills 19 U.S. soldiers at a U.S. military complex in Khobar.
Bin Laden declares jihad against Americans he says are occupying Saudi Arabia.
Nearly 3,000 people are killed in the Sept. 11 attacks by al Qaeda hijackers. Fifteen of the 19 hijackers are Saudis.
Saudi Arabia denies any link to or knowledge of the attacks. A U.S. government commission in 2004 finds no evidence that Saudi Arabia directly funded al Qaeda. It leaves open whether individual Saudi officials might have done so.
Saudi Arabia opposes the U.S.-led invasion of Iraq.
The United States withdraws all remaining combat troops from Saudi Arabia.
Three suicide bombers kill at least 35 people, including nine Americans, in Riyadh, part of a years-long militant insurgency against foreigners and Saudi government facilities.
The Arab world is convulsed by uprisings. Saudi Arabia is concerned by what it sees as President Barack Obama's abandonment of Egyptian President Hosni Mubarak, a U.S. ally.
Saudi royals complain publicly about U.S. policies, including Obama's approach to Iran and Syria.
World powers strike a deal with Iran easing sanctions in return for curbs on its nuclear programme. Riyadh fears this will strengthen Iran.
Saudi Arabia launches a campaign against Iran-aligned Houthis in Yemen, giving Washington only a few hours' notice. The United States however provides military support.
Congress overrides Obama's veto of a law removing sovereign immunity and opening the way for relatives of Sept. 11 victims to sue Saudi Arabia over the attacks.
Saudi Arabia welcomes President Donald Trump's decision to withdraw from the Iran agreement.
In November, the United States condemns Khashoggi's killing at the Saudi consulate in Istanbul.
The United States becomes the world's largest oil producer.
U.S. lawmakers, citing evidence of Saudi Crown Prince Mohammed bin Salman's (MbS) role in the Khashoggi case and incensed over the civilian toll from Saudi air attacks in Yemen, increase efforts to block arms sales to Riyadh. Riyadh blames the killing on rogue operatives, denying MbS had any role.
An attack on Saudi oil installations halves production. Trump says it looked like Iran was behind the attack but stresses he does not want to go to war.
Saudi Arabia signals backing for the Abraham Accords under which its allies the United Arab Emirates and Bahrain forge ties with Israel. Riyadh stops short of recognising Israel itself.
President Joe Biden adopts a tougher stance over Saudi Arabia's rights record. As a presidential candidate, Biden had vowed to make Riyadh a "pariah" over the Khashoggi killing.
Biden declares a halt to U.S. support for offensive operations in Yemen, including relevant arms sales.
In June, Biden says Saudi Arabia had shown "courageous leadership" by backing extension of a U.N.-backed Yemen truce.
With oil prices soaring, the White House welcomes a decision by OPEC+ nations to increase output.
Biden visits Saudi Arabia in a bid to reset ties, but leaves without securing an immediate pledge for more oil supplies.
OPEC+ cuts oil output targets ahead of U.S. mid-term elections, leading Biden to pledge "consequences" for Saudi Arabia and accusing it of siding with Moscow.
The White House welcomes moves by Riyadh to help Ukraine in its war with Russia, and later reiterates its commitment to the kingdom's security.
The Biden administration rules that MbS, as Saudi prime minister, has immunity from a lawsuit over Khashoggi's murder.
In March, Saudi Arabia and Iran agree to restore diplomatic relations in a Chinese-brokered deal. The United States says Saudi Arabia kept it informed about the talks but it was not directly involved.
In March, Saudi authorities release Saad Ibrahim Almadi, a U.S. citizen jailed for 19 years for posting criticism of the government on Twitter, but he remains banned from travelling.
In April, oil output emerges as a point of disagreement again, with the Biden administration telling Saudi officials it disagreed with a surprise OPEC decision to cut production.
After fighting erupts in Sudan, the United States and Saudi Arabia lead efforts to secure a ceasefire.
In May, Saudi Arabia invites President Bashar al-Assad to an Arab Summit in Jeddah, joining a growing number of Arab states to rebuild Syrian ties despite U.S. disapproval.
Ahead of a visit to Saudi Arabia in May, White House national security adviser Jake Sullivan says the United States is working hard to normalise ties between Israel and Saudi Arabia. The top U.S. diplomat for the Middle East, Barbara Leaf, later plays down the prospects of a breakthrough.
(Writing by Tom Perry; Editing by William Maclean and Christina Fincher)