President Barack Obama has signed into law the contentious compromise bill hammered out in Congress, narrowly averting the US \'fiscal cliff\' of tax hikes and drastic, immediate cuts in spending, the White House said early Thursday. In a statement, the White House said that Obama late on Wednesday signed the \"American Taxpayer Relief Act of 2012,\" raising taxes on households earning above $450,000 and delaying spending decisions for two months. Obama also signed into law a $633 billion US defense spending bill that funds the war in Afghanistan and boosts security at US missions worldwide. \"I have approved this annual defense authorization legislation, as I have in previous years, because it authorizes essential support for service members and their families, renews vital national security programs, and helps ensure that the United States will continue to have the strongest military in the world,\" Obama said in a statement early Thursday after signing the measure. Obama said that he signed the measure despite reservations. \"In a time when all public servants recognize the need to eliminate wasteful or duplicative spending, various sections in the Act limit the Defense Department\'s ability to direct scarce resources towards the highest priorities for our national security,\" the president said. \"Even though I support the vast majority of the provisions contained in this Act... I do not agree with them all,\" he said in his statement, adding that he did not have the constitutional authority to approve piecemeal items within the sprawling bill. \"I am empowered either to sign the bill, or reject it, as a whole,\" he said.