Channel tunnel operator Eurotunnel says failure to reach a deal with creditors on a £6.2bn ($11.3bn) debt could hit results for the second half of 2006.
Eurotunnel has said its results are a 'marked improvement'
It came as it said revenues in the first half of 2006 rose 2% to £277m.
It said it "would be an injustice if these efforts were reduced to nothing by the refusal of creditors to reach a rapid solution" on the issue of debt.
Eurotunnel has warned it has two months to avoid bankruptcy after talks with dissident investors on debts collapsed.
It has also asked a French court to freeze its massive debts, so it can continue cross-Channel operations while a court-administered survival plan is established.
Alongside debt talks, Eurotunnel has restructured its fares to compete more effectively with no-frills airlines.
The group also said it had reduced operating costs by 9% to £116m.
Jacques Gounon, chairman and chief executive of Eurotunnel said: "Eurotunnel's operating results for the first half of this year are very good.
"This marked improvement is the tangible result of the considerable efforts made by the staff and shows the potential Eurotunnel has."
The firm has warned that without a debt overhaul, it will not be able to guarantee its future beyond 2007 - the point when it is scheduled to start paying back a significant portion of the debt.
If Eurotunnel goes bust, control of the tunnel is likely to pass to a group of banks.