FRANKFURT (Reuters) - Shares in Linde LIN1.DE dropped as much as 10 percent on Monday after the German industrial gases group's planned $86 billion merger with U.S. rival Praxair PX.N was thrown into doubt by more demands from U.S. antitrust regulators.

The U.S. Federal Trade Commission (FTC) is asking for more assets to be sold than previously anticipated and also wants prospective buyers to meet certain other requirements, Linde said in a statement on Sunday.

“Linde and Praxair are analyzing these expectations to assess their scope and to evaluate how they could be implemented to achieve a timely clearance of the business combination,” it said.

Analysts said the deal was still likely to go ahead, but the risk of it falling apart had risen and, with more forced sell-offs, the benefits had diminished.

“The probability of a no-deal scenario has increased and the synergy potential has been reduced if the deal does go through,” said Sebastian Satz of Barclays.

The regulatory challenge is a setback for Linde Chairman Wolfgang Reitzle, who has been a driving force for the deal and had to reshuffle management following the departure of the company’s chief executive and finance chief.

The planned all-share merger, agreed in principle in December 2016, would create a global leader in gas distribution ahead of France's Air Liquide AIRP.PA, which had also bulked up with the takeover of rival Airgas.

The companies agreed at the time that if regulators demanded the disposal of businesses with more than 3.7 billion euros ($4.3 billion) in sales or 1.1 billion euros in earnings before interest, taxes, depreciation and amortisation (EBITDA), either party could withdraw without penalty.

Based on its discussions with the FTC and other regulators, Linde said there was a higher probability the two companies would need to sell assets exceeding the agreed threshold.

The companies have so far agreed to sell assets to a consortium of German gases firm Messer and buyout group CVC, as well as to Taiyo Nippon Sanso Corp 4091.T, with combined annual sales of about 2.7 billion euros and roughly 700 million euros in EBITDA.

Linde said the companies remained in constructive talks with the regulators and with each other. It declined to comment beyond its statement. Officials at Praxair were not immediately available for comment.

The companies face an Oct. 24 deadline to complete the deal under German financial market rules.

Linde shares were down 9.4 percent at 1306 GMT (9.06 a.m. ET), trading at a three-month low.

Jefferies analyst Laurence Alexander said the companies were likely to get relatively low prices for additional divestments, but put the probability of the deal closing at more than 85 percent.

Reuters reported last month the European Commission was set to give its blessing to the tie-up after an in-depth review.