By Patricia Zengerle WASHINGTON (Reuters) -Legislation that would provide billions of dollars in new security assistance for Ukraine and Israel was blocked in the U.S. Senate on Wednesday as Republicans pressed their demands for tougher measures to control immigration at the U.S. border with Mexico. The vote was 49 in favor to 51 against, meaning the $110.5 billion measure did not obtain the 60 votes needed in the 100-member Senate to pave the way to start debate. The vote was along party lines, with every Senate Republican voting no along with Senator Bernie Sanders, an independent who genera…