Cleveland-Cliffs said on Tuesday U.S. Steel must immediately provide the company and the United Steelworkers (USW) with information about all the proposals it has received so far as a part of its strategic review.

U.S. Steel, which rejected Cliffs' $7.3 billion cash-and-stock offer as inadequate, had earlier said it was exploring "multiple unsolicited proposals".

Under the Right to Bid provision of the labor agreement with the workers union, U.S. Steel must "promptly" notify USW and Cleveland-Cliffs if they receive a proposal from any third party, Cliffs' chief executive Lourenco Goncalves wrote in a letter to U.S. Steel.

The stance comes after the USW said last week it would only back Cleveland-Cliffs as a suitor for the company. The union believes "over the years, Cliffs has shown itself to be an outstanding employer to all of its workers".

Even if U.S. Steel has not received any bids, the company must acknowledge that no such proposals have been received, Cleveland-Cliffs said.

U.S. Steel had also attracted a $7.8 billion all-cash offer from Esmark Inc and a potential acquisition interest from ArcelorMittal SA.

(Reporting by Priyamvada C in Bengaluru; Editing by Krishna Chandra Eluri)