The Indian business tycoons tabled their bid for Liverpool nine months after failing to buy a 51 per cent share in the Anfield outfit.
They join at least four other interested buyers including Chinese businessman Kenny Huang, who has already held talks about buying Liverpool's £237 million debt off the Royal Bank of Scotland.
Huang, backed by the £209 billion Chinese Investment Corporation, was favourite to replace unpopular American owners Tom Hicks and George Gillett.
He is said to be backing boss Roy Hodgson with a £150 million transfer kitty, The Sun reports.
But the Anfield auction is now wide open.
An insider said: "Some potential buyers have declared their interest but haven't tabled a bid, whereas Ambani and Roy have put their money on the table. At this stage Liverpool are happy to let everyone compete against each other to get the best possible deal."
Ambani, valued at around £12.5 billion, while fellow billionaire Roy is head of the Sahara Group, which sponsored the India cricket team.
Hicks and Gillett valued Liverpool at £600 million after Huang's interest emerged.
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