US President Barack Obama called German Chancellor Angela Merkel on Monday to congratulate her on the Christian Democratic Union\'s success in the German federal election on Sunday, the White House announced. \"The President noted his deep appreciation for Chancellor Merkel\'s friendship, leadership and steadfast support of the transatlantic relationship, \" a statement said. \"The President and Chancellor Merkel agreed to continue their close cooperation on key issues of regional and global concern,\" it added. Merkel\'s conservative Christian Democratic Union (CDU) won the elections with some 41.5 percent of votes.