Deep in the Gulf waters between Qatar and Iran lies the world's largest gas field, a 9,700-sq-km expanse that holds at least 43 trillion cubic metres of gas reserves.
Qatar's southern portion is known as North Field, while Iran's slice to the north is called South Pars. The two countries share exploration rights in the area, and its one of many ties that bind them.
But Doha's relationship with Tehran has been put to a new test on Monday, after Iran's regional rival Saudi Arabia led four other countries in cutting diplomatic ties with Qatar, accusing its fellow Gulf Cooperation Council (GCC) member of undermining security in the region by siding with Iran, among other actions.
Saudi also urged "all brotherly countries and companies" to follow its lead in isolating Qatar, a call that GCC members Kuwait and Oman have so far sidestepped.
Saudi said Qatar is supporting "Iranian-backed terrorist groups" in its province of Qatif and in Bahrain, accusations that Doha branded a "campaign of lies that have reached the point of complete fabrication". What's behind the diplomatic breakdown in the Gulf?
Riyadh also said "authorities in Doha" have supported the Iran-backed Houthi armed group in Yemen. This despite Qatar's deployment of an estimated 1,000 troops to support the two-year Saudi-led campaign there.
In an editorial published on Monday, The National newspaper owned by the United Arab Emirates (UAE) government also denounced Qatar's "false friendship" citing the "close ties between Doha and Tehran".
"Iran's actions in the Middle East have cost Doha's Arab neighbours blood and treasure," the editorial said, adding "the regime across the Arabian Gulf is no friend to Doha".
Al Jazeera senior political analyst Marwan Bishara, however, said the accusation "does not hold water", noting Abu Dhabi also maintains diplomatic relations with Tehran.
"And yet it prefers to sever its relationship with Qatar, rather than with Iran," he said.
In a separate statement, the Qatari Cabinet said the measures taken by the five countries against Doha were "unjustified".
"The aim is clear and it is to impose guardianship on the state. This by itself is a violation of its [Qatar's] sovereignty as a state."What’s caused the diplomatic rift?
The spark for this flare-up was a report by the state-run Qatar News Agency that carried comments by Qatar ruler Sheikh Tamim bin Hamad Al Thani criticising mounting anti-Iran sentiment. Qatari officials quickly deleted the comments, blamed them on hackers and appealed for calm.Is this a Sunni vs Shia tension?
Partly. The Shia-led Islamic Republic of Iran is Sunni-led Saudi Arabia’s main regional rival. Why is the spat taking place now?
The temperature noticeably rose following Donald Trump’s visit. Days after Trump and Saudi King Salman bin Abdulaziz singled out Iran as the world’s main sponsor of terrorism, Saudi Arabia and the UAE accused Qatar of trying to undermine efforts to isolate the Islamic Republic. What do analysts say?
Emboldened by closer US ties under Trump, the Saudis and the UAE are seeking to crush any opposition that could weaken a united front against Iraian influence in West Asia. Are disagreements with Qatar anything new?
Qatar hosts Hamas’s exiled leadership as well as Taliban officials. Analysts say Riyadh and its allies want to show Qatar, a country of 2.6 million residents, it is punching above its strategic weight.What are the repercussions for markets?
Any dispute in the region will make oil markets nervous. Internal disputes among the Gulf countries could limit their appeal to foreign investors. Independent foreign policy
Souzan Krdli, a Tehran-based Gulf analyst, said more than demanding Doha's allegiance, Saudi and the UAE want to "rein Qatar in" and make it "another Bahrain if you will" in terms of foreign policy.
"Saudi and the UAE have always been troubled with Qatar's outreach and ambitious diplomacy," she told Al Jazeera.
Krdli, who previously worked at Qatar University, said Doha's relationship with Tehran reflects the country's attempt since 1995 "to carve a policy that is independent of its neighbours".
"This independence was an objective in itself, as well as a means to secure sovereignty" in the face of its larger neighbours, primarily Saudi with whom Qatar has had territorial disputes as recent as 1992, she said.
"The continuation of this independent foreign policy means banking on the economic and diplomatic ties Qatar has forged through investment, natural gas export, diplomacy and mediation."
In the middle of the current rift with Saudi, Krdli said Qatar is also "obliged" to maintain "a middle position" with Iran because of its shared gas exploration in the Gulf.
Krdli also noted unlike previous disputes, when Qatar took immediate conciliatory actions to Saudi and the UAE, Doha is taking a more "defiant" stand this time.
Along with the decision by Saudi to cut diplomatic ties with Qatar, Riyadh has also decided to block air, sea and land transport links.
There have been reports of trucks carrying food shipments from Saudi being blocked at the Qatari border.Mediation not escalation
Sadegh Ghorbani, editor of the Tehran-based Fars News Agency, told Al Jazeera the regional tension is "not welcome by Iran".
"However, it is clear that a rift in the GCC can be beneficial to Iran," he said. "Saudi Arabia is a lifeline for Qatar in terms of trade. We must wait and see whether Iran and Turkey can fill the void."
Already, Iran has offered food shipments to Qatar. Reza Nourani, chairman of Iran's union of agricultural exporters, said such transfers can reach Doha in 12 hours.What's behind the diplomatic breakdown in the Gulf?
Earlier, Iran's foreign ministry spokesman Bahram Ghasemi called for a "clear and explicit dialogue" among the feuding parties, saying tensions would only threaten the interests of everyone in the region.
His statement reflected the social media posts of Iranian Foreign Minister Javad Zarif who wrote, "Neighbours are permanent; Geography can't be changed. Coercion is never the solution. Dialogue [sic] is imperative, especially during blessed Ramadan."
Mahjoob Zweiri, a Middle East expert at Qatar University, told Al Jazeera's Folly Bah Thibault third party mediation is necessary to resolve the "crisis" immediately.
He said Saudi Arabia and its allies cannot leave Qatar without any other options by forcing it to choose sides.
"This is a scenario that will not lead to a solution. If this goes on, this will empower Iran in the region. I don't think Riyadh wants this," Zweiri, a doctorate graduate from the University of Tehran, said.
"I think if there is no mediation, if there is no third party intervening, I think we could see more escalation in this crisis."