European shopping centre giant Klepierre has threatened to complicate Hammerson's £3.4 million tie-up with Intu by making a takeover approach for the Birmingham Bullring owner.
Klepierre, a French property giant with shopping centres in 57 cities across the globe, made a proposed 615p-per-share bid on March 8, but said the move was snubbed by Hammerson in less than 24 hours.
The cash-and-shares approach represented a 40.7% premium of Hammerson's share price on Friday of 437.1p per share.
In a statement to the London Stock Exchange, Klepierre said there was no guarantee that a firm offer would be made.
The move comes after Hammerson agreed an all-share takeover of rival Intu in December last year, which will create Britain's biggest property company.
The acquisition will result in Hammerson shareholders owning 55% of the combined firm and Intu investors the remainder. Intu operates the Trafford Centre in Manchester, while Hammerson owns Bicester Village and Brent Cross shopping centre.
However, the move comes at a tough time for Hammerson, which has been relegated to the FTSE 250 Index after seeing its share price slide in response to market concerns over the woes on the high street.
The tough trading conditions facing retailers have intensified in recent months, with surging inflation and paltry wage growth prompting consumers to tighten their belts.
Hammerson announced last month a 6.9% rise in net rental income for the year to December 31 to £370.4 million, up from £346.5 million a year earlier.