Dates have been fixed at Cardiff’s Principality Stadium on 14 December or a return to Madison Square Garden on 29 November.
A west coast city in the US has also made a late offer to stage the contest.
Two other unnamed countries have also bid for the fight.
Joshua’s team were keen to finalise a date for the bout last week but the offers from new countries have delayed them in confirming Cardiff or New York.
The financial packages put forward in the late bids were lucrative enough to merit discussions, though there is concern the countries in question do not hold a substantial track record in staging high-profile Boxing events.
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Cardiff is the only UK option because the Principality Stadium can offer a roof along with a large capacity during a British winter but Joshua is said to be keen on a return to Madison Square Garden, where his US debut was wrecked by Ruiz in one of heavyweight Boxing’s biggest shocks.
American Ruiz – who fights under a Mexican flag as a result of his heritage – has talked up fighting in Los Angeles or Mexico.
The 29-year-old’s comments and delays in confirming the rematch has led to speculation negotiations have stalled or that the champion was contemplating trying to avoid Joshua.
But Joshua’s promoter Eddie Hearn has said Ruiz would face legal proceedings if he were to pursue another path.