The so-called "Alliance of Yemeni Tribes" was revealed during a ceremony at the headquarters of the First Armoured Division whose leader, dissident General Ali Mohsen al-Ahmad, joined the protest movement in March.
The coalition pledged "to protect and defend... the popular and peaceful revolution" of youths who since January have been holding sit-ins or protesting across Yemen against Saleh's rule, a statement said.
"Any aggression or threat against the (protest) venues... will be considered an attack against the tribes," it added.
Saleh belongs to the Hashid tribe which was a steadfast backer of the regime until it broke ranks with him to join the protest movement in March.
The veteran Yemeni leader has been in hospital in Saudi Arabia since early June for a series of operations on wounds suffered in a bomb attack on his presidential palace.
Between 500 and 600 dignitaries and tribal chiefs attended Saturday's ceremony during which a 116-member consultative council was also formed.
Tribes wield much influence in impoverished Yemen, where the Hashid is a heavily armed tribal confederation capable of rallying and financing thousands of fighters. The Bakil is the other main tribal confederation.
In March, Sheikh Sadiq gave his formal support to the protesters, calling for the ouster of Saleh who has been in power for 33 years.
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