Bankers, traders, support staff in Credit Suisse's investment bank in London, New York, and in some parts of Asia are expected to bear the brunt, with almost all activities at risk, the report said.
UBS intends to eventually reduce the total combined headcount by about 30%, or 35,000 people, with headcount at Credit Suisse currently at about 45,000, the report said, citing people familiar with the matter.
As many as 10,000 jobs would be cut if the Swiss domestic businesses of the two banks are merged.
UBS and Credit Suisse declined to comment.
Reuters had last week reported that UBS will cut Asia investment banking jobs at Credit Suisse next month, with significant reduction in investment bankers covering Australia and China.
Earlier this month, UBS Chief Executive Sergio Ermotti warned of painful decisions about job cuts following the takeover of Credit Suisse, but did not give details about the number of potential layoffs.
UBS completed its emergency takeover of embattled rival Credit Suisse in June, forging a Swiss banking and wealth management giant with a $1.6 trillion balance sheet and a workforce of 120,000.