The 32-year-old former Fulham defender, who has joined on a three-year contract for an undisclosed fee, is the third U.S. international at Rangers with Alejandro Bedoya, 24, who joined from Orebro on Wednesday, and fellow midfielder Maurice Edu.
The Scottish Premier League side have an injury crisis ahead of their first leg against Maribor in Slovenia and said on their website that they hoped Bocanegra would get international clearance in time to make his debut.
The versatile Bocanegra, who has 93 caps, went to the last two World Cups and captained the U.S. at the 2010 finals in South Africa, playing at left-back and in central defence.
He started his career at Chicago Fire in 2000 before joining English Premier League side Fulham in 2004 and four years later moved to Rennes before switching to Saint-Etienne in 2010.
The 24-year-old Bedoya had signed a pre-contract agreement to join Rangers at the end of the Swedish season in January but the clubs reached an agreement for him to join immediately.
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