The NFL has announced sell-outs for its two regular-season games in London in 2013.
Speaking in his annual eve-of-Super Bowl press conference in New Orleans, Commissioner Roger Goodell said: "We are announcing today that our two games on London (in 2013) are already sold out. It is a sign that the game is growing globally."
After six successful games at Wembley Stadium since 2007, the NFL recently confirmed that two games would be played there in 2013, with the Minnesota Vikings hosting the Pittsburgh Steelers on September 29 and the Jacksonville Jaguars at home to Super Bowl finalists San Francisco 49ers on October 27.
All tickets released for sale in the UK have sold out over the past month, with allocations set aside for the competing teams to sell to their local fan-base.
"I think the message is clear," Commissioner Goodell continued.
"There are passionate fans who love the NFL in the UK. There is another step we now need to look forward to.
"What is the next step? Do we move to three games, are there other ways to grow the game in the UK? This is a market where we need to be more active and to grow our game."
Any tickets remaining unsold by teams will be returned for sale to UK fans later in the year.
The Commissioner's announcement comes after further recent signs of significant development in American football in the UK.
For the first time, two British players are expected to selected by NFL clubs when the best college players in the US become available to teams in the annual draft in April.
Manchester's Menelik Watson, an offensive lineman at Florida State University, is projected by some experts to be a first-round selection, while Crawley's Tom Wort, a linebacker at Oklahoma University, is also expected to be picked.
They would join Londoner Jack Crawford, who was drafted in the fifth round last year by the Oakland Raiders.
Earlier on Friday, the British American Football Association (BAFA) announced record participation figures in American football at UK universities, with more than 4,000 members representing more 70 universities