PHILADELPHIA (Reuters) -U.S. President Joe Biden said on Monday that he did not think workers at the nation's three large automakers were likely to go on strike, despite a looming contract deadline later this month. "I'm not worried about a strike," the Democratic president said on Monday as he arrived in Philadelphia ahead of a speech for the U.S. Labor Day holiday. Late last month, the United Auto Workers union said its members voted overwhelmingly in favor of authorizing a strike at the Detroit Three automakers if agreement is not reached before the current four-year contract expires on Sept. 14.