The S&P 500 and the Dow have closed marginally lower after volatile trading as investors swivelled their focus between China-US trade talks, President Donald Trump's threat to shut down the US government and political uncertainty in Britain.

The S&P 500 and the Dow have closed marginally lower after volatile trading as investors swivelled their focus between China-US trade talks, President Donald Trump's threat to shut down the US government and political uncertainty in Britain.