West Ham could be just days away from agreeing a deal to move into the London 2012 Olympic stadium.
Officials at the London Legacy Development Corporation gave an upbeat assessment of negotiations with the premiership club.
A spokesman said: "Things are going well but we're not quite there yet."
West Ham is under pressure to conclude a deal before next Tuesday's LLDC board meeting.
The club is understood to have reached agreement on a key demand from City Hall - a profit-sharing deal if West Ham is sold.
The east London club was first named preferred bidder for the stadium two years ago but the negotiations collapsed amid fears of a legal challenge under European law.
West Ham regards its current offer as "fantastic" for the club and east London.