Alisher Usmanov, one of Arsenal's largest shareholders, has refused to rule in or out a takeover of the club.Red & White Holdings, the investment vehicle for the Russian steel magnate, with a 26.3% stake in Arsenal, has said it will keep all options open. [LNB]Speculation over ownership of Arsenal has intensified after news emerged that Lady Nina Bracewell-Smith had appointed a firm to sell her 15.9% stake. [LNB]Its biggest investor, US billionaire Stan Kroenke could also up his stake. [LNB]However, the prospect of the US sports tycoon, increasing his 29.98% stake in Arsenal appeared to diminish on Tuesday when Mr Kroenke said he planned to take full ownership of the St Louis Rams American football team. [LNB]He already owns the NBA's Denver Nuggets basketball team, the NHL's Colorado Avalanche hockey team and Major League Soccer's Colorado Rapids. [LNB]Multi-ownership[LNB]If either Mr Kroenke or Mr Usmanov bought Mrs Bracewell-Smith's stake, it would take them over the 30% threshold which, under City takeover rules, requires them to make a formal offer for the business. [LNB]Mr Usmanov's Red & White said it remained a "committed long-term investor". [LNB]"At this stage Red & White retains all its options and does not wish for the purposes of the City Code on Takeovers and Mergers to reduce its future flexibility and accordingly no particular course of action is ruled in or out," it said. [LNB]Arsenal shares are currently valued at about £10,000 each. [LNB]The eventual sale of Mrs Bracewell-Smith's stake is also likely to attract interest from new investors, and the club has long supported a "multi-ownership model". [LNB]Arsenal are currently third in the Premier League - with an outside chance of winning the title for the first time since 2004.