Three years ago, an air, land and sea blockade was imposed on Qatar by four Arab countries.
Saudi Arabia, the United Arab Emirates, Bahrain and Egypt cut diplomatic and trade ties with Doha, and imposed a sea, land and air blockade on Qatar, claiming it supported "terrorism" and was too close to Iran.
Qatar rejected the claims and said there was "no legitimate justification" for the severance of relations.
While the Qatari prime minister visited Saudi Arabia last year for a series of summits, the highest-level meeting since the beginning of the crisis, Doha subsequently expressed reservations about the statements issued in Mecca.
"The Gulf summit statement talked about a unified Gulf, but where is it amid the continuation of Qatar's blockade?" said Sheikh Mohammed bin Abdulrahman Al Thani, Qatar's foreign minister.
Here are five things you need to know about the Qatar-GCC crisis:
How it started
On May 23, 2017, hackers posted false statements attributed to Qatar's emir on the Qatari state news agency's website.
The fake remarks, praising Iran and criticising US foreign policy, were picked up and aired on several UAE and Saudi-owned television networks.
The fake news was first posted two days after US President Donald Trump met Arab and Muslim leaders in Riyadh. On May 24, authorities in Saudi Arabia and the UAE also blocked Al Jazeera's website.
On June 5, the Ministry of Foreign Affairs in Bahrain, Saudi Arabia, the UAE and Egypt issued statements announcing the severing of diplomatic relations with Qatar.
Saudi Arabia then shut its land border with Qatar, and together with three other countries imposed a land, sea and air embargo on its neighbour.
The four countries claimed that Qatar worked to support "terrorism", maintained intimate relations with Iran and meddled in the internal affairs of their countries.
Qatar responded by saying that there was "no legitimate justification" for the actions taken by the four countries. It added that the decision was a "violation of its sovereignty" and that it would work to ensure that it would not affect citizens and residents.
The roots of the conflict
A previous diplomatic rift had developed in 2014, when Saudi Arabia, the UAE and Bahrain pulled out their diplomats, claiming that Qatar supported armed groups. However, the border remained open and Qataris were not expelled.
Tensions with Qatar have generally revolved around its alleged support for political Islamic movements, such as the Muslim Brotherhood, as well as complaints about the Al Jazeera Media Network, which is based in Doha.
These tensions were exacerbated by the Arab Spring in 2011 when Saudi Arabia and Qatar were seen as backing different sides.
On June 7, 2017 the Saudi foreign minister said that Qatar must cease its support of groups such as Hamas and the Muslim Brotherhood.
Blockading countries' demands
The four countries issued a list of demands to be carried out within 10 days, which Qatar promptly rejected.
At the top of the list was downgrading of diplomatic ties with Iran, but it also included ceasing military cooperation with Turkey and shutting down Al Jazeera.
These countries also called on Doha to sever ties to "terrorist groups" and stop the funding of persons and groups designated as "terrorists" by the US and other nations, and to stop alleged meddling in other states' affairs.
Qatar's economy has proven resilient amid the blockade and lower oil prices, the International Monetary Fund said ahead of the two-year anniversary.
"Economic performance improved in 2018. Qatar's economy has successfully absorbed the shocks from the 2014-16 drop in hydrocarbon prices and the 2017 diplomatic rift," the International Monetary Fund (IMF) said in a statement.
The fund estimated real GDP growth at 2.2 percent, up from 1.6 percent in 2017, and also said the country's banking sector was healthy, although it reported a cooling in the housing market.