Westfield founder Frank Lowy believes it’s the appropriate time for a $US25 billion ($A35 billion) sale of his shopping centre empire and is ‘100 per cent comfortable’ with the move.

The 87-year-old described this week’s announcement as ‘bittersweet’ as the company prepares to sell its 35 UK and US operations to European shopping centre owner Unibail-Rodamco.

It is one of the largest corporate deals in Australia’s history.

‘The most important thing is that this transaction is in the best interest of shareholders,’ Mr Lowy, who will step down as chairman, said in London.

‘That principle has guided my decision making since 1960.’

Westfield’s Australian centres, which are managed by the separately listed Scentre Group, are unaffected.

Mr Lowy will remain an active investor, chairing an advisory board for Unibail-Rodamco that will offer strategic advice, while his sons Peter and Steven will retire as co-chief executives.

The takeover will make Unibail-Rodamco the world’s largest shopping centre owner, with 104 shopping centres in 13 countries, all of which will now carry the Westfield brand.