Eurotunnel, the firm which operates the Channel Tunnel, has warned its revenues this year may not be enough to cover interest repayments.
The group blamed a fall in passenger numbers following stiff competition for the shortfall.
Its revenues fell 7% in the first six months of the year, from £292m a year ago to £272m.
Underlying losses at the firm also widened by 2% to £79m.
"Our first half results reflect the current depressed demand and consequent pricing pressures which are affecting the travel and freight transport sectors as a whole," said chairman Charles Mackay.
Bleak outlook
Eurotunnel said it had managed to reduce its debt in the past six months by £90m.
But it warned that the current weak demand would continue in the next six months.
Passenger numbers fell to 2.8million from 3.2million a year ago.
"These challenging market conditions now look set to continue in the second half.
"As a result of the continuation of these difficult market conditions, we are now unlikely to achieve the full year revenues needed to cover our interest charges from cashflow," warned Mr Mackay.