Ticket sales for the latest NFL game in London have been suspended because of a legal dispute involving one of the participants, the St Louis Rams.
The Rams were due to take on the New England Patriots at Wembley on 28 October, but their stadium lease requires all of the team's home games to be played in St Louis.
The team recently agreed to switch one home game to the UK for three years.
NFL commissioner Roger Goodell said he was optimistic of resolving the issue.
Competitive games have been played in London since 2007 and the NFL announced last autumn that it was going to stage at least one match per season in the UK until at least the 2016 season.
The dispute centres on a clause in the Rams' lease agreement on the Edward Jones Dome.
Goodell promised UK fans of American football that they will still have a game in 2012 but acknowledged that the line-up may have to be changed.
"We're going to play the London games," he said. "We hope it will be with the Rams and the New England Patriots. That's what we planned... but there are issues that obviously are going to have to get resolved.
"We know there are discussions going on. We hope they will get resolved shortly."
A statement on the NFL UK website said: "The reason for the postponement is to allow the Rams and their stadium authority time to finalise the technical amendments to the lease required under the terms of the Rams' commitment to London.
"The Rams have expressed optimism that a resolution is near, and we will provide updates as information becomes available."