Media mogul Sumner Redstone has reached agreement with his daughter, Shari, to put some of National Amusement's 1,500 cinemas on the block rather than the entire division, as part of debt-restructuring discussions to avoid selling more shares of Viacom (NYSE: VIA.B - News) and CBS, according to people familiar with the matter.

If lenders agree, the plan would clear the way to sell a part of the US group and 19 theatres in the UK. A prospectus is not expected to be released until early January, one person familiar with the discussions said.

National Amusements, which also houses Mr Redstone's controlling stakes in Viacom and CBS, owns theatres in Latin America and Russia. The company is expected to hold on to theatres in the New England area, where National Amusements is based and which account for about half of the US-group's value.

It was not immediately clear how much the proposed partial sale would fetch. The entire chain is valued at $500m to $700m by analysts and at about $1bn by Mr Redstone.

The sale is part of discussions with lenders to restructure $1.6bn in debt, about half of which matures on December 19. The due date could be extended if lender talks progress, people familiar with the matter have said. Mr Redstone in October breached a debt covenant tied to the market value of Viacom and CBS after the stock price of both had fallen precipitously, forcing the 85-year-old mogul to sell $233m of non-voting shares of the two companies.

Viacom and CBS shares have fallen by 66 per cent and 74 per cent respectively since the beginning of the year as investors fret over their exposure to a weakened advertising market.

National Amusements last week sold its 87 per cent stake in video game company Midway for $100,000 and the assumption of $70m in debt to a private investor. Mr Redstone rushed to sell before the end of 2008 in order to realise a net tax loss of $800m that can be applied against income earned this year and prior years.

Also probably up for sale is National Amusement's controlling stake in WMS, a slot-machine company.

Mr Redstone has vowed to sell no more shares of Viacom or CBS.