A UK panel has set an 11 September deadline for bidders to make a formal offer for troubled rail operator National Express or risk a lengthy delay.
The panel has said if the bidders do not make their offers by the set deadline, they will have to hold their bids by at least six months.
The rail operator is up for takeover after it reported losses and a $1.7bn debt that forced it to give up its East Coast Rail franchise.
A consortium of CVC group and Spain's Cosmen family has shown interest in the rail operator, in which the Cosmen family already owns almost a 19% stake.
Negotiations now rest on whether or not the UK Department for Transport will allow National Express to retain its C2C franchise to the east of London and the East Anglia franchise, both of which have made losses.
The CVC consortium has said that it will only buy the operator if it can keep the two franchises as well as extend the East Anglia part of the agreement.