RIO TINTO has stepped up its canvassing of shareholders to determine what changes will be needed to secure their approval of the group’s controversial $US19.5 billion  refinancing compact with China’s state-owned Chinalco. Rio has formally left open the prospect of it recasting the deal to see off criticism from shareholders that since the deal was struck in February, it has become too generous to the Chinese. There has been particular concern over the pricing of the $US7.2 billion convertible bonds in the deal.