A Canadian-led consortium bidding to buy water giant Severn Trent is considering pulling out after its third offer was rejected.
The £5.3 billion bid, valuing Severn at £22 a share, was dismissed by the firm's board within hours of being tabled on Friday.
Severn, which supplies 4.2 million customers across the Midlands and parts of Wales, said it failed to recognise the long-term value or future potential of the company.
It means the LongRiver consortium must decide whether to put in a new, fourth offer before the expiry of Tuesday's 'put up or shut up' deadline or to walk away.
The bidders, comprised of Canadian investment group Borealis, the Kuwait Investment Office and Universities Superannuation scheme, previously had a £4.96 billion bid rejected.
It is thought that the consortium has grown increasingly concerned at what it perceives as the water company's lack of engagement with it.
Rejecting the latest offer on Friday, Severn's chairman Andrew Duff said: "We have held private conversations with LongRiver and made clear that we have no objections to fuller discussions in the event that LongRiver puts forward a proposal which properly reflects the long term value and future potential of Severn Trent."
But he added that the board unanimously agreed that the bid was not high enough.
It was reported that an increase of around 40p a share would be enough to bring Severn to the table.
But LongRiver is thought to be determined that there must be a meeting with the water firm's board before any move can take place.
British water companies are prized by investors such as pension funds, sovereign wealth groups and private equity firms for their monopoly over customers and relatively stable earnings, which are tied to inflation.
Severn is the latest British utility to attract interest after buyouts for rivals Yorkshire Water, Northumbrian Water and Thames Water.
Borealis already co-owns the UK's biggest ports operator Associated British Ports and the London to Paris High Speed One rail line.
It invests on behalf of thousands of Canadian workers and pensioners in the Ontario Municipal Employees Retirement System.
The Kuwait Investment Authority invests the emirate's vast oil wealth, while the Universities Superannuation Scheme invests the pensions of UK higher education workers.