LONDON -- Olympic Stadium officials made their preferred pick for a full-time tenant on Wednesday, selecting Premier League football club West Ham as the top choice to move into the east London venue in 2016.

West Ham will now enter into exclusive negotiations over the terms of a 99-year lease that would allow the club to move 3 1/2 kilometres from its 35,000-capacity Upton Park to a stadium slated to be downsized from 80,000 seats at the Olympics to 60,000.

The company tasked with securing the Olympic Park's future named West Ham as the preferred partner for the 486 million pound (C$775 million) stadium after determining that the club "ranked highest of the bids."

The London Legacy Development Corporation board rejected bids from third-tier football club Leyton Orient and a group that hoped to stage Formula One races. But London Mayor Boris Johnson warned that West Ham would only be allowed to move into the stadium if he is satisfied with the financial package being offered.

Besides paying annual rent, West Ham owners David Gold and David Sullivan would have to give the London legacy company a share of any profit if they sell the club.

The legacy company said the stadium needs more than 150 million pounds of building work -- including adding retractable seating to cover the running track, a roof and facilities for fans -- for West Ham to play there.

West Ham would have to fund part of the transformation of the stadium.

"There is a lot negotiation still to go on about exactly the terms," Johnson said.

"If we can't do a deal that protects taxpayer value, that protects the Olympic investment of half a billion pounds building the stadium, then that's fine," Johnson said. "It's a question of making sure that the value of the public asset is properly reflected in the commercial deal that is now being done with a private sector entity."

West Ham vice chairwoman Karren Brady said it would only accept a proposal that would "right for the club and our supporters."

"This includes the necessity of agreeing a stadium design specification that is acceptable to us in terms of its ability to host world-class football matches," Brady said.

If a deal cannot be done with West Ham, the stadium would be used for athletics, concerts and community events. Officials hope matches will be staged there during the 2015 Rugby World Cup, but that wouldn't be feasible if the stadium was being turned into a football-viable venue.

The world championships in athletics will be held at the stadium in 2017.

"I can see a great future for the stadium with or without association football," Johnson said. "It's a very considerable state asset."