By Andrea Shalal and Steve Holland WASHINGTON (Reuters) -U.S. President Joe Biden on Saturday authorized an additional $200 million in weapons and other assistance for Ukraine, the White House said, as Ukrainian officials said heavy shelling by Russian forces were endangering attempted evacuations of civilians. The decision brings total U.S. security aid provided to Ukraine to $1.2 billion since January 2021, and to $3.2 billion since 2014, when Russia annexed the Crimea region of Ukraine, according to senior administration officials. In a memorandum to Secretary of State Antony Blinken, Biden…