U.S. reviews military presence in Europe after Russian moves in Ukraine

U.S. President Barack Obama (R) is greeted by Poland's President Bronislaw Komorowski upon his arrival in Warsaw June 3, 2014. REUTERS/Kevin Lamarque

WARSAW (Reuters) - The United States is reviewing its military presence in Europe as a result of Russia's intervention in Ukraine, the White House said on Tuesday at the start of a four-day European trip by President Barack Obama.

Obama will call on Congress to support a "European Reassurance Initiative" of up to $1 billion to increase U.S. military rotations on the continent, it said.