Rugby World Cup organisers have been given another month to decide whether London's Olympic Stadium is to be one of the venues for the 2015 tournament.
England Rugby 2015 had expected to agree a final list of venues with the International Rugby Board on Friday, but an extension has now been granted.
West Ham United are the preferred tenants to take over the stadium, but a final deal with the London Legacy Development Corporation has yet to be agreed by the football club.
Tournament organisers are keen to include the stadium, but the venue's uncertain future has so far prevented them from making a firm decision.
A RWC statement said: "Both parties agreed that appropriate time should be given to allow every possible opportunity to include the Olympic Stadium, one of the world's most recognisable venues.
"The additional time will enable England Rugby 2015 to finalise negotiations and scheduling with other venues."
England Rugby 2015 chief executive Debbie Jevans added: "We are determined to select the best venues and deliver the optimum schedule for the Rugby World Cup, and are delighted to have received such strong support from the RWC Limited board for our proposals.
"Our plans are on track and we are confident that we will finalise the schedule and the venues in the next few weeks."
The current capacity of the Olympic Stadium, which cost £486m to build, is 80,000.