The lending arrangement, comprising a £200m loan and an £850m credit facility that can be called upon if required, now runs until May 2014.
Shares in Thomas Cook rose around four per cent when the London Stock Exchange opened after the statement.
Last week, the firm said profits would be hit by unrest in the Middle East and North Africa, and by weak UK spending.
The group also warned that the interest margins on the facilities had been reduced with immediate effect. The rate is now 2.25 per cent on the loan, and between two and 2.5 per cent on the credit facility, depending on how much is used. The margin had previously been 2.75 per cent for both facilities.
The group is currently looking to sell some hotels and other assets, worth an estimated £200m, as it seeks to reduce its debt. Finance director Paul Hollingworth said Thomas Cook had around £900m of available cash and committed facilities.
He said: “We are focussed on reducing our debt and strengthening our balance sheet and we have a number of initiatives underway to deliver progress on this, including the disposal of certain hotel and surplus assets.”
The company has been hit by disruption to a string of its holiday destinations, including Tunisia and Egypt.
Its French business had been paticularly badly hit, it admitted. The company is now estimating profit for the year to 30 September of around £320m while the City had pencilled in a figure of £380m.
However, Thomas Cook said average UK selling prices for summer holidays were up four per cent as more customers bought packages that included food. Despite the “difficult trading conditions”, bookings by UK customers are up by one per cent for the key summer season. The company said it was resisting raising holiday prices because customers were so cash strapped.