The BBC, one of the world's leading news organisations, is expected to announce job losses that will eventually see its World Service cut by a quarter.
It follows an announcement on Wednesday that it is to close five of its services - the Albanian, Macedonian, Serbian, Caribbean and Portugese for Africa services in a bid to save £46 million a year.
BBC Global News director Peter Horrocks said the closures were not a reflection on the performance of individual services, but were needed because of the scale of the cuts to its grant from the UK Foreign and Commonwealth Office.
Mr Horrocks is expected to announce that about 650 jobs will be lost over three years - one quarter of World Service staff, the BBC reports.
The National Union of Journalists has written to the chairman of two parliamentary committees, urging them to review what it called the "drastic cuts".
In October last year, the British government announced that the BBC would take over the cost of the World Service from the Foreign Office.
The service, which started broadcasting in 1932, currently costs £272 million a year, and has an audience of 241 million worldwide across radio, television and online.