The 400 jobs would translate to less than 2.5 percent of UBS's overall investment bank, which employed 16,432 people at the end of June.

The cuts are planned for corporate finance fixed income and equities across all the Swiss bank's regions, the source said.

A spokesman for UBS declined to comment.

UBS pledged last year to cut 3,500 jobs across the whole bank including flagship wealth management operations as part of earlier cost cuts. But analysts say this is not enough, given a dramatic slowdown in investment banking business and tighter capital rules governing riskier business.

A Swiss newspaper reported on Sunday that UBS is to shed 900 jobs in information technology, alongside a further 2,000-4,000 layoffs in its investment bank and other central functions. UBS reports third-quarter earnings on October 30.

Separately, the Financial Times reported on Wednesday that UBS's board met in New York on Tuesday to hammer out details of a restructuring, but that cuts might not be finalized in time for third-quarter earnings because various options are still being weighed.

The FT also reported that UBS's investment bank was looking to continue exiting capital-intensive areas in fixed-income trading such as long-end flow rates and global correlation trades.

(Reporting By Katharina Bart; Editing by Erica Billingham)

• A Permanent Economic Emergency