Qatar's Emir Sheikh Tamim bin Hamad Al-Thani attended the Gulf Cooperation Council summit in Kuwait City but was not joined by the leaders of the UAE and Bahrain, also part of a Saudi-led boycott of Qatar.
The future of the six-nation GCC -- formed 36 years ago to bring together the energy-rich Sunni-led Gulf Arab states -- appeared to be hanging in the balance.
This year's meeting comes six months into a rift between Qatar and the Saudi-led bloc, the worst crisis ever to hit the organisation.
The Qatari emir accepted an invitation, but just hours before the talks began, Saudi King Salman sent his foreign minister, Adel al-Jubeir, in his stead.
State television showed Kuwaiti Emir Sheikh Sabah al-Ahmad Al-Sabah receiving Jubeir at the airport as the head of the kingdom's delegation.
Sheikh Sabah, whose country has been leading thus far unsuccessful mediation attempts to resolve the crisis, said Kuwait would continue its efforts.
"We have been stormed in the past six months with painful and negative developments... but we managed to achieve calm," Sheikh Sabah said in his address opening the summit.
"Our meeting today is a reason to continue the mediation which fulfils the ambitions of our people."
He called for the GCC charter to be amended to establish a clear mechanism for resolving disputes between member states.
Kuwait Foreign Minister Sheikh Sabah Khaled Al-Sabah later told a news conference that "the holding of the summit amid these delicate situations proves the faith and conviction of GCC leaders in this organisation".
The meeting, scheduled to last until Wednesday, was cut to a single day.
The UAE's state minister for foreign affairs Anwar Gargash told AFP on the sidelines of the summit that it had taken place under "sensitive circumstances and is a positive step".
Bahrain sent its deputy premier to the meeting.
The three Gulf states, together with Egypt, cut all ties with Qatar on June 5, accusing the gas-rich emirate of supporting Islamist extremists and of being too close to Shiite Iran, Riyadh's arch-rival.
Qatar denies the allegations and has accused the Saudi-led bloc of aiming to incite regime change in Doha.
Casting further doubt on the group's future, the UAE said Tuesday it was forming a new military and economic committee with Saudi Arabia separate from the GCC.
The committee "will coordinate between the two countries in all military, political, economic, trade and cultural fields," according to a decree issued by UAE President Sheikh Khalifa bin Zayed Al-Nahyan.
Founded in 1981, the GCC is a political and economic union grouping Qatar with Bahrain, Saudi Arabia and the United Arab Emirates as well as Oman and Kuwait.
GCC future in doubt
Dominated by Riyadh, it has been a regional counterweight to Iran.
On Monday, the foreign ministers of Saudi Arabia and Qatar attended round-table talks ahead of the gathering, in their first such encounter since the diplomatic crisis erupted in June.
After cutting off all ties with Qatar, Saudi Arabia and its allies imposed a land, sea and air blockade of the emirate and issued a list of 13 demands to have it lifted.
Bahrain in October called for Qatar's membership of the GCC to be suspended until it accepted the demands.
Those present at Tuesday's meeting managed to agree on one issue, strongly condemning Yemen's Shiite Huthi rebels for killing former president Ali Abdullah Saleh.
They called for Yemenis to "get rid of the Huthi militias which are following and being backed by Iran."
The GCC condemned "all terrorist actions carried out by Iran and its continued interference in the internal affairs and Arab countries".
But despite member states' broad agreement over Iran, experts have warned that the Qatar crisis could lead to the demise of the once-powerful GCC.
"The justifications for the existence of the GCC bloc amidst the continued crisis are no longer present like before," said Sami al-Faraj, head of the Kuwait Center for Strategic Studies.
"As long as our enemy has changed from Iran to Qatar, the GCC will not continue."
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)