By Jeff Mason, Bart H. Meijer and David Brunnstrom WASHINGTON/BRUSSELS (Reuters) -U.S. President Donald Trump opened a new phase on Monday in the trade war he launched this year, telling partners, from powerhouse suppliers such as Japan and South Korea to minor players,

After months of threats, President Trump is abruptly re-escalating the trade war.For businesses craving certainty, who've had a period of relative calm, the move could once again upset that balance.It also injects a new risk into financial markets that have largely already moved on to a post-tariff world.