By Patricia Zengerle WASHINGTON (Reuters) -An emergency spending bill to 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, leaving the $110.5 billion measure short of the 60 votes needed in the 100-member Senate to pave the way to start debate, threatening President Joe Biden’s push to provide new aid before the end of 2023. The vote was along party lines, with every Senat…