Around 190 jobs could be moved offshore by American Express under proposals put out to consultation.
The firm is looking at migrating some non-customer-facing roles at its operations centre in Brighton, East Sussex, to India and Argentina.
The multi-national financial services company is Brighton and Hove's biggest private sector employer with 2,900 staff working in the city and 3,500 across Sussex.
A company statement said Brighton "continues to be an important part of our global network and we remain committed to the city".
It is building a new European operations centre there and has switched more than 150 jobs from Madrid to Brighton.
It said: "As a global company, we are always seeking ways to make our business more flexible and efficient to help better serve our customers.
"This approach sometimes involves moving some functions from one operations centre to another.
"No final decisions have been made in relation to the proposal, which could potentially impact approximately 190 permanent roles.
"More details will be available following the appropriate consultation period. It would, therefore, be inappropriate to comment further at this stage."
The company said it will provide support to employees affected by the plans over the coming weeks.