Industrial machinery maker Gardner Denver Inc has ended talks with SPX Corp and has invited the private equity firms that made offers for the company to re-engage in a sale process, a source familiar with the matter said on Friday.

Talks between SPX and Gardner Denver ended after doubts emerged on both sides about the deal's success, the source said. Private equity firms have now been asked to meet with Gardner Denver management in early January, the source added, speaking on condition of anonymity because the discussions are confidential.

Gardner Denver passed on all-cash offers in the mid-to-high $70s per share range from private equity firms Advent International Corp, KKR & Co LP and a consortium of TPG Capital LP and Onex Corp , people familiar with the matter told Reuters last week.

Gardner Denver declined to comment, while SPX did not immediately respond to a request for comment. Advent and TPG declined to comment, while KKR and Onex did not immediately respond to a request for comment.

The talks between Gardner Denver and SPX focused on an SPX offer of around $85 per share for Gardner Denver, a source familiar with the matter said earlier this week.

(Reporting by Greg Roumeliotis in New York; Additional reporting by Michael Erman in New York; editing by John Wallace)