Lawyers representing relatives of victims who died in a mid-air plane crash last year in Swiss-controlled airspace are demanding millions of francs in damages.
German lawyers Michael Witti and Gerrit Wilmans are calling for around SFr150 million ($109 million) to be put into a special compensation fund.
The German lawyers have threatened to take the matter to court if no settlement is reached.
The legal team claims the Swiss air traffic control agency, Skyguide, is partly to blame for the accident over southern Germany that claimed 71 lives.
The collision in July 2002 involved a Russian passenger plane and a cargo jet belonging to DHL. The dead included 52 Russian schoolchildren travelling to a Unesco conference in the Spanish city of Barcelona.
They said German air traffic control, the courier company, DHL, and the Russian firm, Bashkirian Airlines, also bore some responsibility.
While official investigations into the accident continue, attention has focused on the contradictory instructions given to the pilots by Swiss air traffic controllers in Zurich.
Skyguide reacted with astonishment to the news of the multimillion-franc demand.
Communications director Rosemarie Rotzetter said the lawyers had not informed Skyguide's legal team about the claim. The first the company had heard of the demand was through reports in the media, she said.
Rotzetter said that blame for the tragedy had not yet been apportioned. She stressed that, in any event, Bashkirian Airlines would be first in line to pay damages to the victims' relatives, payouts which would be covered by insurance.
Skyguide is 99 per cent owned by the Swiss government and on Wednesday the finance ministry said it would not comment on the issue of compensation payouts due to ongoing negotiations with relatives.
Spokesman Daniel Eckmann said, however, that Switzerland wanted to reach a fair settlement with relatives as soon as possible.
It was in November last year that Witti, a class-action specialist, first announced that he would be seeking many millions of dollars in compensation for those bereaved by the crash.
Witti said he would try to bring an action on behalf of his clients in the United States because the country had "a much more friendly law for victims".
swissinfo with agencies
The Swiss air traffic controller, Skyguide, is being asked to contribute to a compensation fund totalling aorund SFr150 million ($108 million).
The fund would aid relatives of those killed in a plane crash over southern Germany.
The accident occurred in Swiss-controlled airspace in July 2002.
The lawyers, who represent the families of 40 Russian victims, say they will pursue the matter in court if no settlement is agreed.