The six-nation Gulf Cooperation Council (GCC) hosts its annual summit in Riyadh on Tuesday amid signs of a thaw between Qatar and Saudi Arabia, which has led an economic boycott of its neighbour since 2017.
Saudi Arabia and allies Egypt, Bahrain and the United Arab Emirates closed their airspace to Qatar Airways and banned travel to the country under the blockade.
Here's a look at the two-and-a-half-year crisis ahead of what could be a "reconciliation" summit.
What triggered the spat?
Even before the crisis erupted, relations between Qatar and its giant neighbour Saudi Arabia were rocky in recent years, in part because of Qatari TV network Al Jazeera's critical coverage and Doha's support for Arab Spring uprisings.
In June 2017, the Saudi-led group formally cut off ties, accusing Doha of backing radical Islamists, including the Muslim Brotherhood, and seeking close ties with Iran.
Qatar, a tiny gas-rich emirate, vehemently denies the charges and has accused Riyadh of "bullying".
The regional schism has seen the two sides trade barbs on everything from access to the Muslim holy city of Mecca to alleged Twitter hacking.
It has also seen families divided and Qatari businesses face increased costs as well as complicated regional travel and diplomatic efforts.
The Riyadh-led bloc has said the crisis will not end until Qatar accepts its list of 13 demands, including that it shut down Al Jazeera, downgrade ties with Iran and close a Turkish military base in its territory.
Doha has refused to bow to the demands.
Why is there a push to end the crisis now?
Analysts say the spat has hurt the blockading countries more than Qatar.
Saudi Arabia now appears to be taking a de-escalatory approach after adopting a combative foreign policy under de facto leader Crown Prince Mohammed bin Salman.
A cool reception by global investors to state energy giant Aramco's stock sale has highlighted the downside of its aggressive stance, observers say.
But some of the other blockading countries are not as eager to step back.
Two sources familiar with the negotiations, including an Arab diplomat, told AFP that hardliners in Abu Dhabi — Riyadh's principal ally — are opposed to a restoration of ties.
This has raised the prospect of a "bifurcated peace", implying Qatar could possibly normalise ties with only some blockading nations, including Saudi Arabia, with whom it shares its only land border.
For now, analysts say the rapprochement appears to be shaping up without major concessions from Doha after the blockade boosted its self-reliance even as it has deepened losses at flag carrier Qatar Airways.
Could the GCC summit spell the end of the rift?
The summit could turn out to be a "reconciliation" conference, leading to a breakthrough, especially if Qatar's Emir Sheikh Tamim bin Hamad Al-Thani takes part.
Saudi Arabia's King Salman sent him a personal invitation but it was unclear so far whether the emir — who left for Rwanda on Monday — would attend.
Some Saudi observers have downplayed the king's invitation to the emir, saying he was only following protocol and that he had invited the Qatari leader to last year's summit as well.
But regional analyst and King's College London assistant professor Andreas Krieg said he believed Riyadh had pushed for the gathering to be shifted from the UAE to Saudi Arabia to increase the likelihood of the emir attending.
Even if the emir does not attend, Qatar is likely to send high-level representation and negotiations to end the impasse are expected to continue.
"Ending the Gulf rift is an incremental process of engagement and dialogue rather than something resolvable at a single summit meeting alone," said Kristian Ulrichsen, a fellow at Rice University's Baker Institute in the United States.
Does football diplomacy play a role?
As the row involves the host nation of the 2022 World Cup, many of the peace overtures centre on football.
The diplomatic crisis invigorated a campaign by Qatar's critics to strip Doha of the 2022 World Cup, but the efforts have not borne fruit so far.
In a U-turn, three boycotting countries — Saudi Arabia, the United Arab Emirates and Bahrain — participated in the recent Gulf Cup football tournament in Qatar.
Leading Emirati politics professor Abdulkhaleq Abdulla, an authority on the UAE's political thinking said the end of the boycott could be in sight following the Gulf Cup announcement.
Abdulla called the decision "as political as it is sporting".
"Football… may open the door for the travel of sports fans to Qatar to support their teams, which means necessarily lifting the travel ban to Qatar and the return of Gulf cohesion," he said on Twitter.