Shelbourne's planned Chicago Spire aims to be the tallest residential building in the world

Shelbourne Development is in talks with a large US trade union about funding its stalled Chicago Spire project. Shelbourne, owned by Garrett Kelleher, put the building, which will be the tallest residential building in the world, on hold after the basement was completed.

A spokeswoman for Shelbourne confirmed to the Sunday Tribune that talks were under way with union AFL-CIO, but would not say whether the union would merely finance the tower's construction or take an equity stake in the development. Talks have been under way since January but the Chicago Tribune reported last week that they were still in the "embryonic stages".

The union is attracted by the idea of the number of construction jobs that will be created if the project goes ahead and the fact that construction would take five years. AFL-CIO has three pension funds that invest in projects and it is unclear at this stage which fund would invest in the project if agreement is reached.

Shelbourne says it has sold about a third of the apartments. Kelleher has invested about €140m of his own money in the venture, with Anglo Irish Bank also providing finance. It was reported recently that the project requires €1.3 billion of funding to complete.

The Shelbourne spokeswoman confirmed that liens against the project, including one from architect Santiago Calatrava for $11m, are still in place and being negotiated.