A multi-billion dollar submarine deal between long-standing allies - Australia, the UK and the US - has come under the spotlight after the Trump administration said it was reviewing how the deal fits in with its heavily-touted "America First" agenda.

Congressional Democrats condemned the review as casting doubt over the strength of America's alliances with Britain and Australia.

The Trump administration may try to squeeze more concessions out of Australia as part of “the art of the deal,” but it does not want to spike the relationship entirely.