Mr Usmanov is Arsenal's second-biggest shareholder
A spokesman for Russian billionaire Alisher Usmanov has called on fellow Arsenal shareholder Stan Kroenke to reveal his intentions for the club.
On Monday, US billionaire Mr Kroenke raised his stake to almost 30% - the point at which he would be forced to make an offer for the whole club.
A spokesman for Mr Usmanov's Red and White Holdings said Mr Kroenke should say if he intends to launch a takeover.
Mr Usmanov is Arsenal's second-biggest shareholder with a 26% stake.
"Mr Kroenke has never taken the opportunity to reassure the fans and it would be good for the club's stability if he were to do so," the spokesman told the BBC.
Mr Kroenke bought 25 more shares in Arsenal this week for £212,500, or £8,500 a share, and is within 17 shares of the threshold that would force a takeover bid.
The market price for Arsenal shares is currently about £9,000.
Under takeover rules, any public statements regarding future bid intentions must be unambiguous, otherwise the individual concerned would be prevented from making a formal takeover move for six months.
Earlier this month, Mr Usmanov bought 61 shares at £9,200 a share.
The spokesman for Red and White Holdings said Mr Usmanov was a long-term investor and would continue to pick up shares as and when they became available.