The company that owns One World Trade Center has sued a steel firm for holding "hostage" the structure designed to top the building, according to media reports. ADF Steel Corporation, a Canadian structural steel fabricator, refuses to deliver the antenna as part of a separate contract fight.

"ADF refuses to ship this antenna steel unless and until it receives approximately $6 million allegedly owed under another project, as ransom," the Port Authority said in the complaint.

The antenna would be about 400 feet high and will play a key role in determining the ultimate height of the building. Earlier this year the developers changed the design of the spire, raising questions about whether the structure would be included when the CTBUH determines the architectural height of the building. The CTBUH includes spires and architectural elements in its measurements, but not antennas and temporary structures.

ADF previously promised it wouldn't withhold steel for the spire, which costs $10 million, regardless of the previous contract dispute, according to the lawsuit.

About 100 ironworkers could be laid off if "they have no steel to erect," the Port Authority said. The situation has reportedly already delayed the building's schedule, the media reports.