MOSCOW (Reuters) - A decision by the British people to quit the European Union in a forthcoming referendum would trigger a period of uncertainty for the world, BP <BP.L> Chief Executive Bob Dudley told Bloomberg TV on Friday.

Speaking on the sidelines of the St Petersburg International Economic Forum, Dudley said: "It's not going to change exactly what BP does. We will respond.

"(But) my personal concern is the unintended consequences - no one is quite sure what will happen. I'm sure the pound will gyrate a bit. I think it will put the world into some period of uncertainty ... including for Britain. So, I'm concerned about that," he said.

(Reporting by Vladimir Soldatkin; Editing by Andrew Osborn)