Keira Knightley admires Angelina Jolie's devotion to charitable causes.

The 'Begin Again' actress recently went with Oxfam to visit a refugee camp in South Sudan to help the organisation raise awareness in their battle against poverty - but thinks it would be tough to do as much for others as the 'Maleficent' star, who is also a special envoy for the United Nations (UN).

Speaking to the Daily Telegraph newspaper, Keira said: ''I admire Angelina Jolie hugely.

''I don't think I could ever be anything like as impressive or authoritative as she is on the world stage.

''She's pretty much devoting her life to her causes, and that's a great thing, a great message. I'm always happy to help in any small way I can.''

As she met refugees, Keira was asked who she was, and felt embarrassed at saying 'actress' rather than ''something else useful''.

She explained: ''When those refugees asked me, 'Who are you?', I really, really wished I could have said, 'I'm a doctor', or something else useful.

''So instead I told them, 'I am somebody who is going to ask people to give lots of money to Oxfam, so they can help you.' ''