Spanish media are linking the Philadelphia Union teenager as a potential target for Barca, raising the prospect of a potential battle for one of the most exciting talents in U.S soccer.
At this stage, sources indicate there is no active consideration for an alternative destination at this stage. It is believed that Sullivan is focused on his development in MLS and with the United States national team before he then makes his move to England.
The 17-year-old has already agreed to join City, with a move set for January 2028, when he will be eligible to make the switch across the Atlantic.
The existing arrangement remains in place, despite the anxious wait for the Manchester club to discover their punishment for being found guilty of breaches of Premier League financial rules.
Sullivan's future at City will be more thoroughly assessed closer to the time of his anticipated move.
Discussions are expected to later determine whether he is ready to compete for a place in Enzo Maresca's first-team squad or benefit more from a loan spell to gain more experience in senior European football.
So far, though, he is showing incredible progress.
His performances for Philadelphia Union and the USMNT have continued to underline his status as one of the country's brightest young prospects, following his rapid rise.
Sullivan is a confident player who will show clear focus on how his career opens up.
For now, Philadelphia retain control of his immediate future and they intend to make the most of his time at the club.
They are enjoying a strong period in MLS, with no defeats since returning from the World Cup break across 13 matches.
This is a great time for Sullivan and while Barcelona's reported interest adds another layer to his story, the current expectation remains that his pathway will still lead towards City.