The 23-year-old enjoyed an outstanding 2021 season for the MLS Cup and Eastern Conference champions, claiming the Golden Boot with 22 strikes in 35 appearances across all competitions.
Castellanos has continued his impressive form in 2022, netting 11 times in 17 games in the MLS and CONCACAF Champions League.
A number of European clubs including Everton, West Ham United, Newcastle United and Bologna are believed to be interested in the Argentine, who still has three years remaining on his NYCFC contract.
However, LeedsLive claims that Jesse Marsch's side are also looking to sign the striker and club officials including Orta and Kinnear have been spotted just a few miles away from the Yankee Stadium, with transfer talks set to take place.
Leeds are keen to bolster their attacking options this summer after Patrick Bamford endured an injury-hit 2021-22 campaign, which left the Whites with limited options up front.
Marsch has already added midfielder Brenden Aaronson to his squad for next season, while Red Bull Salzburg right-back Rasmus Kristensen is believed to be closing in on a move to Elland Road.