Barclays is expected to announce up to 15,000 job cuts as part of its new strategy due to be announced later, according to BBC business editor Kamal Ahmed.
That is significantly above the 10,000 to 12,000 the bank has already announced it wants to cut this year.
A large proportion will be in the UK - as high as 70%, our correspondent said.
Although the job losses will be mostly in the investment bank, Barclays' retail operation will not be immune.
Barclays' chief executive, Antony Jenkins, would like to see the global workforce of the bank fall over the next six years from 140,000 to 100,000, according to our correspondent.
On top of cutting staff, Barclays is expected to announce that it will be hiving parts of the business that have not been performing well into what is known as a "bad bank".
A cut in the number of branches is also likely. At the moment Barclays has 1,600 branches, but that could fall by 400 over the next few months. However, an announcement on that is not thought to be imminent.
Instead, the investment bank is likely to be the focus of attention later.
It has been hit by a slowdown in the demand for government and company debt - or bonds.
Investment bank income was down 28% in the last quarter, in large part down to a 41% fall in the trading of bonds.
Overall Barclays' first quarter pre-tax profits were down 5%.
The bank's shareholders have been unhappy about bonus payments at the bank, given falling profits.