WASHINGTON (Reuters) - U.S. President Donald Trump on Friday told British Prime Minster Theresa May the United States would continue to help the United Kingdom thwart attacks, the White House said in a statement after a blast on a London commuter train earlier in the day. In a telephone call with May, Trump expressed support for those injured and  pledged to continue close collaboration with the United Kingdom to stop attacks worldwide targeting innocent civilians and to combat extremism,  the White House said. 