Here is a summary of the situation in parts of the Middle East where Iran and Saudi Arabia have been involved in proxy conflicts and which could be affected by a Beijing-brokered deal to re-establish relations between the two regional powers.
Riyadh intervened in Yemen at the head of a Western-backed coalition in 2015 against the Houthi movement after the Iran-aligned group ousted the internationally recognised government from power in the capital, Sanaa.
The war has been in military stalemate for years. The Houthis, de facto authorities in North Yemen and holding areas of its border with Saudi have launched repeated missile and drone strikes on the kingdom, which has tried to extract itself.
Riyadh and the Houthis last year resumed direct talks, facilitated by Oman, following a U.N.-brokered truce. The truce lapsed in October but has largely held.
Restored ties between Riyadh and Tehran could facilitate an agreement between Saudi and the Houthis.
The Yemen war has also been a point of tension with the United States under President Joe Biden's administration, which has slapped restrictions on U.S. arms sales to the kingdom.
Iran has offered military, economic, and diplomatic support to President Bashar al-Assad since his crackdown on protests in 2011 left him isolated.
China also provided cover for Syria at the United Nations and kept up economic and political ties with Damascus.
Early on, Riyadh backed insurgents trying to topple Assad to weaken Tehran. But as Iran's support helped Assad turn the tide, Saudi backing for the armed and political opposition has waned.
The Saudi-Iranian deal comes as Arab isolation of Assad is thawing. Saudi has said more engagement could lead to Syria's return to the Arab League.
Syria's foreign ministry welcomed the deal as an "important step" that could boost regional stability. The opposition's umbrella body did not comment.
Israel, which wants to normalize relations with Saudi, has struck Iran's positions in Syria.
Lebanese politics have been broadly split for years between a pro-Iran alliance led by the powerful armed group Hezbollah and a pro-Saudi coalition.
In 2021, Saudi and other Arab Gulf states withdrew their ambassadors over what they said was Hezbollah's hold over the state.
The envoys returned but Lebanon has since sunk deeper into a financial meltdown and now faces an unprecedented political crisis, with no president for months and a cabinet operating with limited powers.
The rapprochement between Tehran and Riyadh has sparked hope that paralysis could end. Parliament Speaker Nabih Berri said the "positive reading" of the news should prompt Lebanon's politicians to "quickly" elect a president.
Hezbollah said the deal was a good development but cautioned its full implications were still unknown. The group backed Christian politician Suleiman Frangieh for president but two sources say Saudi opposes him.
After the toppling of Saddam Hussein in the U.S.-led invasion of 2003, Iran deepened its political, security, and economic influence in Iraq, sparking Saudi alarm.
In 2019, Iran launched a drone attack on Saudi oil facilities that flew through Iraqi airspace. The following year, the re-opening of a Saudi-Iraqi border crossing after more than two decades prompted hopes of improved ties.
Baghdad has hosted direct talks between its two neighbours but they stalled last year as Iraq faced a political crisis.
Baghdad welcomed the deal as a way to "turn the page". Iraqis hope for a general regional detente that would allow their country to rebuild, instead of being destabilised by U.S., Gulf Arab, and Iranian score-settling.
Friction between Iran and the West has also played out in Gulf waters, through which much of the world's oil transits.
There were several attacks on tankers there in 2019, after then-U.S. President Donald Trump abandoned a nuclear pact with Iran and re-imposed sanctions on it. Seeking to de-escalate, the United Arab Emirates and Saudi began engaging directly with Iran.
The U.S. Fifth Fleet, based in Bahrain, has seized shipments of weapons suspected to have come from Iran. Iran and Israel have also traded accusations of attacking each other's vessels in recent years.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)