I'm an Indian working in a MNC. As a result, I often have to attend(and contribute) to meetings where I have to listen to people who have a pronounced American accent. Some are still understandable, but a couple of people I have interact with speak such a different form of English, I mostly have to guess at what they are saying. When I ask them to clarify, they often speak the same sentence in the same tenor/speed, so my net gain is zero.

My question is, how to politely put it across that due to their accent, I can't understand a thing, and may they please speak slowly and a bit clearly ? Some people might take it a bit personally, since "everyone else" is understanding them perfectly...and I don't want to cause offense at all. Any ideas ?