Eddie Jones insists saving Saracens from relegation will be "toughest challenge" of his career.
Jones lost eight of his last nine Tests in charge of Australia
The former Australia coach has accepted a consultancy role with the Guinness Premiership strugglers, who last week axed director of rugby Steve Diamond.
Sarries lie fourth from bottom, just seven points off last place.
And Jones said: "Given the threat of relegation, it is going to be my toughest challenge - but one I am looking forward to facing."
Jones, who guided Australia to the 2003 World Cup final where they lost to England, was sacked as the Wallabies' coach in December.
But the former Brumbies coach will not be able to join the north London club until 7 March because he is leading an IRB review into coaching standards in the Pacific Islands.
He will stay with Saracens until the end of the season before taking up a three-year contract at Australian Super 14 side Queensland Reds.
"Originally, I was coming over for a couple of weeks to do a review of the club and offer some ideas on how to improve things.
"I know that the Premiership - particularly at this time - is a physically- grinding league and I realise how tough it's going to be," Jones also told the London Evening Standard.
"I will do whatever I can to support (head coach) Mike Ford. Maybe it will help having someone come from outside to take a fresh look at the way things are being run.
"I accept that some of the things I suggest may not work, but it's a case of putting forward ideas because the threat of relegation is serious."
The 46-year-old added he would like to eventually take up a permanent post in England.
"While I am committed to Queensland I would, at some point in the future, like to coach full-time in England," he added.
"It's one of the toughest competitions in world rugby and it's a challenge I would enjoy."
Jones, who took over as Australia coach in 2001, was replaced by John Connolly in December.
"I have moved on, although it did knock me around a bit," he admitted.
"However, it is true that when one door closes another opens and I am excited about the prospect of working at Saracens.
"I couldn't be more enthusiastic about coming to the club."