The 27-year-old has been training with his prospective new team-mates on Wearside for several days, but his move from Estudiantes is yet to go through because of an administrative issue which is a growing concern.
Angeleri qualifies for an EU passport through his Italian father and therefore will not need a work permit.
However, the document is yet to be issued and that is a complication Bruce admits he could do without as he attempts to re-shape his squad for the new season.
He said: "With Marcos, the big problem when you are trying to sign them, of course, is work permit issues.
"He has got an Italian father and he is waiting for an Italian passport. We were told a month ago it was going to be here in within 10 days.
"That's obviously a concern to me because we were told we were going to get it three weeks ago and it's still not here.
"We will look at it and we will have a conversation again with the agents and see where we end up."
Should the transfer go through, Angeleri would be the fourth new arrival at the Stadium of Light this summer with Paraguay international midfielder Cristian Riveros, Belgian goalkeeper Simon Mignolet and loan signing Ahmed Al-Muhammadi already on board.
Bruce, whose side launch their pre-season campaign against Munster XI in Limerick this evening, is currently awaiting an answer from former England defender Sol Campbell, and has several other irons in the fire with defence currently his main focus.
However, he is not looking for a direct replacement for skipper Lorik Cana, who made a shock move to Turkish side Galatasaray last week after just 12 months with Sunderland.
Bruce is confident that in Riveros, Lee Cattermole and Jordan Henderson he has the men to cover for the Albania international despite the long-term absence of promising Irishman David Meyler with a serious knee injury.
He said: "The one thing I am gutted about is the injury to Meyler, because he had a wonderful end of the season and had put big pressure on Cana with his performances.
"But with Riveros coming and Cattermole and the emergence of Jordan Henderson too, I wasn't really that fussed.
"He had a wonderful start to his career here, but found the Premier League physically very difficult towards the end.
"He walked in on the first morning with his father and said he wanted to go an play nearer his homeland of Albania, and wanted to go to Turkey.
"I am always a believer that if somebody is not happy and wants to go back and be nearer his family - there were issues with his family, who needed visas and couldn't get here from Albania - so we have reluctantly let him go."