"Liberty Steel will shortly begin a detailed due diligence and thus gain insight into key business data of Thyssenkrupp's steel business," Liberty said in a statement.
Last week, sources told Reuters that Thyssenkrupp was likely to give Britain's Liberty Steel, headed by metals tycoon Sanjeev Gupta, access to the books of its steel unit.
Gupta's hand has been strengthened due to consolidation talks between Sweden's SSAB and Tata Steel that could result in a deal and potentially leave Liberty Steel as the sole bidder for Thyssenkrupp Steel Europe.
Thyssenkrupp, which confirmed it had agreed to open its books to Liberty, has said it aims to make a decision on whether to sell or keep its steel unit by March.
Deutsche Bank estimates a Liberty Steel-Thyssenkrupp deal could yield synergies of 200-300 million euros and regulatory hurdles are lower than in potential transactions the German group could pursue with Salzgitter or Tata Steel.
"Both companies would complement each other via becoming a stronger player in the Western and Central European markets which particularly Liberty needs to build exposure to increase access to (automotive) clients and realise its decarbonisation strategy," the bank said in a note last week.
A successful bid would cut Liberty Steel's reliance on up to 3 million tonnes of slab and hot rolled coil it needs to buy each year to feed its manufacturing lines. Thyssenkrupp's Duisburg plant, in turn, would be better utilised.
(Reporting by Eric Onstad in London and Christoph Steitz in Frankfurt; Editing by Jan Harvey and David Evans)