U.S. President Barack Obama said Saturday that Republicans in the House are blocking a bill that would prevent a tax increase on the first $250,000 of income earned by all Americans. The Democratic-controlled Senate has approved the measure, but Obama said House Republicans have “put forward an unbalanced plan that actually lowers rates for the wealthiest Americans." Obama supports a plan to raise taxes on families earning more than $250,000. In his weekly radio and Internet address, Obama said “the math just doesn't work" on the GOP plan. Obama's comments mark the fourth time since his re-election that he has used the radio address to push for middle-class tax cuts as part of a plan to avert a looming fiscal cliff — and his most sharply partisan tone. Obama said his plan to raise taxes on the wealthiest Americans should come as no surprise to Republicans or anyone else. “After all, this was a central question in the election. A clear majority of Americans — Democrats, Republicans and independents — agreed with a balanced approach that asks something from everyone, but a little more from those who can most afford it," Obama said. His plan is “the only way to put our economy on a sustainable path without asking even more from the middle class," Obama said. It also is the only plan he is willing to sign, the president said. Obama said in his address that he stands ready to work with Republicans on a plan that spurs economic growth, creates jobs and reduces the national deficit. He said he wants to find ways to bring down health care costs without hurting seniors and is willing to make more cuts in entitlement programs such as Medicare.