SIX American bodies representing big-name brands, clothes retailers and importers have upbraided Australia's top wool body for failing to heal industry splits over ending mulesing, a practice that has led to retailer boycotts by animal activists in the past.

Gap, Macy's and Liz Claiborne Inc are among the companies that have expressed ''great disappointment'' over Australian Wool Innovation's decision to walk away from an industry group writing a response to the Americans detailing how the practice will be phased out by 2013.

''As the face of Australian wool around the world … AWI's withdrawal now calls into question whether the industry is capable of providing any kind of response and represents, in our view, a considerable setback to any potential progress …'' the companies said in a letter.

Mulesing, surgically removing part of a sheep's rear to prevent potentially fatal flystrike, led People for the Ethical Treatment of Animals (PETA) to start a boycott in the US seven years ago.

American textile companies have since set deadlines for Australian woolgrowers to find alternatives, leading to deep rifts that have rocked AWI.

It withdrew from the latest attempt to write a response for the Americans after Victorian and Queensland farmers' representatives refused to endorse a draft that deleted all mentions of the word ''mulesing.''

The vice-president of the US National Retail Federation, Erik Autor, who has been a negotiator with Australian woolgrowers, said that the letter to AWI was intended to send a message to the entire wool industry.

He has warned that many American retailers and brands were taking ''the path of least resistance,'' directing suppliers to use only New Zealand or South African wool. He said the industries in those countries, ''whether accurately or not, have [been] successfully promoted as a non-mulesed alternative to Australian wool''.

AWI's chief executive, Stuart McCullough said woolgrowers were experiencing one of the worst flystrike outbreaks in memory.