A London-based NFL team could be worth more than £100m a year to the UK, says a study published on Wednesday.
Compiled by accountants Deloitte, it says the two NFL games at Wembley in 2013 brought an extra £32m to London.
That could rise to £58m if, as expected, the "International Series" expands to four games a year from 2016.
But the real goal is a full-time London team by 2022, which would mean at least eight games a season, bringing in £102m, according to Deloitte.
The report was launched by Sajid Javid, the Secretary of State for Culture, Media and Sport, and comes a week after Chancellor George Osborne said he would do everything he could to relocate a team to London permanently.
This support is likely to include the type of tax breaks that have been offered to major sporting occasions such as London 2012, the 2014 Commonwealths and next year's Rugby World Cup, but not to one-off athletics, golf and tennis events.
With rates of income tax lower in the US than in the UK, the lack of such a deal for a London team would cause problems for the league and its relationship with the National Football League Players' Association.
The NFL operates under a collective bargaining agreement between the team owners and the players which limits the total amount each team is able to spend, but also sets minimum salaries based on each player's time in the league.
The agreement, effectively a revenue-sharing deal, also restricts a player's contractual freedom, which could result in problems with European Union employment law.
The BBC understands NFL bosses have started negotiations with the European Commission for an exemption, and not just for one team - if a London franchise was to get off the ground, the NFL would look at expanding elsewhere, with Germany the most likely next venue.
Wembley staged its first International Series game in 2007 and hosted single games every year until 2013, when two games took place.
With seven of those eight contests being sell-outs, the decision was taken to expand the series to three games this year and next.
"The NFL games at Wembley have been a huge success showing that there is a big, growing fan-base for the sport in the UK," said Javid. "If the NFL decide that the time is right to base a team overseas, London and the UK will welcome it with open arms."
The Detroit Lions beat the Atlanta Falcons on Sunday and the Dallas Cowboys, one of the sport's most iconic names, play the Jacksonville Jaguars on 9 November.
This means 17 of the NFL's 32 teams will have played at Wembley by next month, with clubs being given bye-weeks to recover from the time difference, although these measures would not be possible for a London team in the current 17-week regular season.
But with the Football Association also very keen on having American tenants at Wembley, the chance of a £100m annual windfall for the UK economy and no sign of the novelty wearing off for British NFL fans, the case for a London franchise could prove irresistible.
|NFL at Wembley|
|2007: New York Giants 13-10 Miami Dolphins (Attendance: 81,176)||2013: Pittsburgh Steelers 27-34 Minnesota Vikings (83,518)|
|2008: San Diego Chargers 32-37 New Orleans Saints 83,226)||2013: San Francisco 49ers 42-10 Jacksonville Jaguars (83,559)|
|2009: New England Patriots 35-7 Tampa Bay Buccaneers (84,254)||2014: Miami Dolphins 38-14 Oakland Raiders (83,436)|
|2010: Denver Broncos 16-24 San Francisco 49ers (84,254)||2014: Atlanta Falcons 21-22 Detroit Lions (83,532)|
|2011: Chicago Bears 24-18 Tampa Bay Buccaneers (76,981)||2014: 9 November - Jacksonville Jaguars v Dallas Cowboys|
|2012: New England Patriots 45-7 St Louis Rams (84,004)|