The holy Islamic pilgrimage to Mecca is the newest frontier in Iran and Saudi Arabia’s ongoing clash over Yemen. Iran announced this week that it was suspending all pilgrimages to Saudi Arabia, where an estimated 500,000 Iranians travel each year to participate in the umrah pilgrimage to Islam’s holiest sites, in what experts said was a “major escalation” of the rivalry between the two regional heavyweights.

A spokesperson for Iran’s Culture Ministry told state TV on Monday that the decision to halt the pilgrimages was a result of the alleged abuse suffered by two male Iranian pilgrims traveling through Jeddah last month, the Associated Press reported. However the move was only announced less than a week after an Iranian plane carrying 260 pilgrims was turned away from the kingdom by Saudi aviation authorities, who claimed it did not have permission to use the country’s airspace.

These recent developments around the pilgrimage are “a reflection of the very deep hatred between the Saudis and Iranians that even go beyond a state of war,” said Ghanem Nuseibeh, a Middle East analyst and partner at Cornerstone Global associates in London. “Even Israeli Arabs are allowed to visit the holy places in Saudi, and Saudi and Israel are at an official state of war,” he said, noting that the decision to halt the pilgrimages was a “major escalation” in dynamics between the Sunni kingdom and the Shiite republic.

The wrangling may be a product of growing tensions stemming from the Saudi-led airstrike campaign in Yemen that has targeted Iranian-backed Shiite rebels. But it is also a reminder of the politicization that has long existed around the pilgrimage to Mecca, which Saudi Arabia administers.

Saudi Arabia strictly enforces a ban on political expression during the pilgrimage but the kingdom has also shown itself willing to use the rite, and its position as gatekeepers to Islam’s holiest sites, for its own political purposes, said Ali Al-Ahmed, a Saudi expert and the director of the Institute for Gulf Affairs in Washington.

“Saudis use their control of Mecca and Medina as a political tool and access to the hajj [pilgrimage] as a reward or punishment for political differences with many countries,” Al-Ahmed argued. “It has been a very effective tool by the Saudis to deter criticisms of its government by Muslims. I have come across a lot of people who say they don't want to criticize Saudi Arabia publicly because they want to go hajj.”

Although all able-bodied Muslims are required to make the hajj pilgrimage to Mecca once in their lifetime, the kingdom has a record of depriving its opponents of access to the holy city. Islamist radicals who espouse views at odds with the kingdom's, including Tunisian opposition leader Rachid Ghannouchi and Kuwaiti preacher Tariq al-Swaidan, are the most notable victims of this practice. Al-Swaidan, who has identified himself with the Muslim Brotherhood movement vilified by the kingdom’s rulers, was prevented from entering the holy city for the umrah pilgrimage in 2013 after he criticized the military-led coup in Egypt. Saudi Arabia was one of the most vocal supporters of the coup, which deposed Egypt’s first democratically elected president, the Muslim Brotherhood leader Mohammed Morsi, bringing to power a military-backed regime led by current President Abdel Fattah al-Sisi.

The perception that Saudi Arabia’s leaders use access to the pilgrimage as a political tool is widespread enough that even logistical adjustments to accommodate ongoing construction efforts at the Mecca pilgrimage site, have been interpreted by some governments as political retaliation. When Saudi Arabia asked several countries in 2013 to temporarily reduce the number of pilgrims they sent to the annual hajj pilgrimage, prominent political figures in Turkey angrily attributed the move to Saudi retaliation against their government’s political stance.

“The hajj issue has links to the political disagreements between [Turkey and Saudi Arabia],” Turkish deputy opposition leader İhsan Özkes said in an interview with the Turkish news site Today’s Zaman. “In previous years, Turkey sent over 70,000 pilgrims to the holy lands. But what happened this year for Saudi Arabia to reduce the number? It is no secret that Turkey and Saudi Arabia have opposing stances on Egypt's coup and that this has affected the hajj issue as well.”

Instances like these have underscored for many Saudi Arabia’s willingness to capitalize on its control of the holy cities for their own political gains. As a result, the pilgrimage has seemed to only be open to those Muslims who do not openly challenge Saudi authority, according to Madawi Al-Rasheed, a visiting professor at the Middle East Center at the London School of Economics.

“Access to Mecca is subject to a strict visa-application process, the purpose of which is to eliminate potential troublemakers such as Iranian pilgrims who have in the past defied Saudi rules and regulations,” Al-Rasheed wrote in a commentary for Al-Monitor. “While many Muslims abide by these conditions, a small minority is always ready to defy the Saudi ban on politics, inviting serious confrontations with the Saudi security forces deployed during the season.”

This dynamic became especially prominent in the aftermath of Iran’s 1979 Islamic Revolution, when many Iranian pilgrims began to use the hajj as an opportunity to stage rallies calling for the “disavowal of infidels,” that denounced Israel and Saudi Arabian ally the United States. The standoff between the Saudi government and Iran on the issue culminated in the 1987 clashes between Saudi security forces and Iranian pilgrims that left 400 dead. Iran blocked pilgrimages for three years following the violence, while Saudi Arabia decided to restrict pilgrim numbers in a move that observers noted was clearly aimed at the Islamic Republic.

As bitter as relations currently are between Iran and Saudi Arabia, they are unlikely to approach the level of hostility of the late-80’s period, said Al-Ahmed who argued that Saudi Arabia was likely to try to rein in any further escalation on the pilgrimage front to prevent tainting the perception of their successful custodianship of the holy cities. “These are the most valuable religious assets in the world and the Saudis use that to promote and expand their soft power,” he said. “Their whole legitimacy is based on religion and this really comes in handy when it comes to regional policies.”