The BBC could axe parts of its sports coverage and a digital channel, it has been reported.
In an interview with the Daily Telegraph, the network's new chairman, Lord Patten, signalled the cuts could materialise but said he would fight to save the World Service from spending cuts.
Lord Patten of Barnes, Britain's last governor of Hong Kong, said the BBC would not be the same once network changes are introduced later this year as part of a 20% budget loss.
The former Conservative Party chairman said the Arabic, Somali and Hindi World Service networks are "at the core of what the BBC is doing" and he will urge Foreign Secretary William Hague to protect the World Service.
Lord Patten ruled out publishing individual stars' salaries.
He also said more cuts to pay for executives would be unveiled; promised to "police" the watershed rigorously and signalled that digital TV channels BBC3 or BBC4 could be axed and one of the main sports events lost.
He told the newspaper: "We have to try to make sure that the BBC is regarded as more efficient than is the case today."
He stressed concrete decisions had not been made.
"I think we're bound to face some tough decisions in the area of sport," he said.
"It's extremely difficult for the BBC to bid for as many sports rights as it would like."
It emerged yesterday that up to 1,500 jobs could be lost in BBC News.