title: U.S. tip-off helped Russia thwart 'major' terrorist plot: White House
text: WASHINGTON (Reuters) - U.S. intelligence agencies provided advanced warning to Russia about a major terrorist plot in St. Petersburg, allowing Moscow to thwart an attack that could have killed  large numbers of people,  the White House said on Sunday.  President Vladimir V. Putin of Russia called President Donald J. Trump today to thank him for the advanced warning the United States intelligence agencies provided to Russia concerning a major terror plot in Saint Petersburg, Russia,  the White House said in a statement. 