The Premiership side have been sharing Watford football club’s ground since 1997 and had an agreement, in principle, to stay there until 2017.
But the Hornets chose to exercise a break clause in May, meaning the coming season will be Saracens’ last at the stadium unless they can strike a new deal.
Watford chief executive Julian Winter said: “We have given them a couple of proposals around a future lease and their response will be back to us by 3 September.
“I think we have to know where we are. That is what we have agreed. We need some certainty with Saracens so we can crack on and plan with or without them.”
Sarries are keen to boost their average attendance and played some matches at Wembley last season because of its increased capacity. The club often struggled to attract large crowds to Vicarage Road, however.