Scotland international had a loan spell with the club last season. United would need to do a loan unless Reading agree to a termination.
McNulty is surplus to requirements and is in the final year of his contract. Former boss Micky Mellon at Tranmere is also interested.
McNulty, 28, for wasn’t really deployed as a main striker under Mellon but has been assured that will be the case under new Dundee United boss Tam Courts.
United have agreed a fee with German Bundesliga 2 side Ingolstadt for Niskanen.They have also thrashed out terms with the 23-year-old and the deal is now subject to a work permit being issued.United men were keen on the winger when he was at KuPS but he decided to head for Germany.
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