
Stan Kroenke, who joined the club's board in September 2008, has purchased 90 additional shares at £8,500 ($13,800) each to add a further 0.2 per cent to his existing holding.
An Arsenal official club statement read: "Stan Kroenke has a beneficial interest in, and controls voting rights over, 17,957 ordinary shares in the Company, representing 28.9 per cent of the company's issued ordinary shares."
The Denver Nuggets basketball team owner is the Gunners' largest shareholder, with Uzbek businessman Alisher Usmanov also holding a share of more than 25 per cent.
If Kroenke reaches a 29.9 per cent threshold it will trigger a formal takeover bid for the club.
Meanwhile, New Birmingham City owner Carson Yeung has pledged to spend up to £40 million ($65m) on new players during the January transfer window.
Yeung made the announcement as he was officially unveiled as the new owner at St Andrew's after completing his £81.5million takeover of the Premier League club.
And the Hong Kong businessman has also given his support to manager Alex McLeish -- saying he will work closely with him to make City "as big as possible".
Yeung told a news conference: "What is the target for Birmingham? Maybe 10th or ninth this season, maybe better next season, not to be a yo-yo club anymore.
"Our aim is to work hard to secure our position in the Premier League, not only for this year but for many years to come.