Van Persie was granted an extended break after his World Cup exertions with Netherlands and began training with United on August 4, but the striker was never expected to be fit enough to feature in last Saturday's shock 2-1 defeat to Swansea City.
But with United under pressure to get their Premier League campaign off and running, the 31-year-old took to Twitter on Thursday to declare himself fit to feature at the Stadium of Light.
Good training session done this morning. Looking forward to sunday! pic.twitter.com/kbeZTx7TOU— Robin van Persie (@Persie_Official) August 21, 2014
New £16 million signing Marcos Rojo also trained with the rest of the United squad for the first time since his move to Old Trafford was confirmed on Wednesday evening.