Sky News can reveal that GVC Holdings is this weekend finalising the details of a long-term joint venture with MGM Resorts International, owner of famous Las Vegas brands including the MGM Grand, Bellagio and The Mirage.
City sources said the deal, which will ultimately encompass online sports betting and other interactive gaming services across the US, could be announced as soon as Monday.
Although the partnership will not involve the two companies swapping equity, insiders said it was "logical" to suggest that a successful alliance could eventually lead to a full-scale merger to create a global gambling behemoth.
Their new joint venture, made possible by a liberalisation of US gambling legislation, is expected to be structured as a 50-50 operation into which both companies will commit an initial $100m (£76m).
The deal will marry GVC's technology expertise and platforms with the footprint and brand of MGM, one of the world's biggest hospitality groups.
It is likely to include a commitment of around 25 years from GVC and MGM, with an option in their agreement to buy each other out after 10 years, according to one source.
The deal will get under way in Nevada, the only state where sports betting remained legal after the passing of laws in 1992.
GVC and MGM will then expand the partnership to other states which legalise the pastime, with as many as 15 likely to do so in the near future.