All eyes are on Chicago, as a Maryland business executive bids to top Alden Global Capital's takeover of Tribune Publishing.

Stewart Bainum Jr is reported to have bid US$650 million (A$840 million) for the whole group.The sum is ten times what he was to pay for Tribune's Baltimore Sun, and is a bid to 'top and stop' the US$630 million offered and agreed with Alden, known in the industry for its harsh asset cuts. The offer emerged in a filing to the US Securities and Exchange Commission earlier this week in which shareholders freed Bainum from a confidentiality agreement so he can talk about - and gain support for - a full counter-offer.

Failing that, the Tribune board had agreed the Alden offer. It was suggested that under Bainum, Tribune's future could be as a not-for-profit.

Tribune owns a range of metro mastheads also including the Chicago Tribune, Orlando Sentinel and New York Daily News.

Alden is already the largest shareholder in Tribune, with 31.6 per cent and three seats on its board.

Last February, Tribune made a nonbinding agreement for Bainum - who is chairman of Choice Hotels International - to acquire the Baltimore Sun, (Annapolis) Capital Gazette and Carroll County (Maryland) Times.

• Bainum may now be joined by two further investors. Swiss billionaire Hansjörg Wyss and tech investor Mason Slaine each say they will contribute US$100 million to Bainum's bid.

Florida-based Slaine, who holds 3.4 per cent of Tribune Publishing, says his interest is in the two mastheads in his home state, the Orlando Sentinel and (Fort Lauderdale) Sun Sentinel.

Tribune's board - on which Alden has three seats - is currently backing the Alden bid despite the higher offer. An earlier version of this report referred to Philadelphia in error.