Deutsche Bahn is considering buying travel and shipping group TUI AG to merge the Hapag-Lloyd container shipping unit with its logistics unit, Reuters reported.
The acquisition would help keep Hapag-Lloyd - which TUI has said it will sell or merge this year amid shareholder pressure to do so - in German hands.
The Financial Times Deutschaland, without citing any sources, said that until now only top level management at both companies was familiar with the plans.
A Deutsche Bahn spokesman said: "This is nonsense."
A TUI spokesman declined to comment.
TUI shares fell 0.6 percent by 0716 GMT, lagging a 0.2 percent dip in Germany's blue-chip index .GDAXI.
The newspaper reported that a key role in the takeover scenario is being played by Juergen Krumnow, who is TUI's supervisory board chairman and also sits on the supervisory board of Deutsche Bahn.
Deutsche Bahn buying TUI would prevent a split up of the shipping and tourism company, the newspaper said, adding that TUI's travel business TUI Travel would mesh well with Deutsche Bahn's portfolio.
Earlier this month, Deutsche Bahn, one of the world's biggest transport groups, saw its path to partial privatisation cleared when the co-governing Social Democrats (SPD) resolved a tortuous debate on the terms.
SPD Chairman Kurt Beck said party leaders had agreed to a slimmed-down privatisation of Deutsche Bahn's rolling stock and logistics, cutting the upper limit of the flotation to 24.9 percent from a previous 49.9 percent.