The American businessman Stan Kroenke has increased his stake in Arsenal and is now within 10 shares of the threshold that forces him to make a takeover bid.

Kroenke, who owns 29.9% of Arsenal, acquired seven more shares yesterday at a cost of £8,500 each, the London club confirmed in a statement to the London stock exchange today. If the Denver-based businessman reaches 30%, he has to make an offer for the remaining shares in Arsenal Holdings plc.

If Kroenke manages to acquire more than 50% of the shares, he will gain legal control of the club. If he reaches 90%, he can compulsorily purchase the remaining shares.

But if he fails to surpass the 50% level, he is prohibited from making another takeover bid for at least a year – unless asked to do so by the club.

The Russian businessman Alisher Usmanov – Arsenal's second-largest shareholder – signalled his interest in a takeover in December by taking his stake beyond 26% through his investment vehicle Red and White Holdings. Unlike Kroenke, Usmanov has not been invited on the board of directors.

Kroenke, who first bought a 9.99% stake in Arsenal in April 2007, also owns the Colorado Rapids of Major League Soccer, the NBA's Denver Nuggets and the NHL's Colorado Avalanche.

Arsenal remain in contention for the Premier League and Champions League titles this season.