President Barack Obama is betting that his re-election gave him the political clout to force Republicans to accept higher taxes on upper-income Americans as a step toward reducing the federal deficit.

In positioning for advantage in negotiations on the fiscal cliff, Obama has been replicating some of the tactics used in his successful campaign for a second term, including speeches, meetings with stakeholders and using social media to make his case to voters. On Monday, the president spent about 45 minutes answering questions on Twitter's microblogging service.

"Keep pressure on Congress," Obama wrote at the end of the session in which he repeated his main arguments for raising taxes on top earners as a start for a plan to cut the deficit. "Call, email, tweet your member."

Republicans have rejected Obama's proposal, which Treasury Secretary Timothy F. Geithner laid out for congressional leaders last week, to avert a so-called fiscal cliff. It had more than $600 billion in spending cuts and tax increases starting to take effect in January.

Geithner offered a reprise of the president's previous budget proposals, with $1.6 trillion in tax increases and about $350 billion in health care savings, primarily in Medicare. He also asked for an Aug. 1 deadline for decisions on an income-tax overhaul and further spending cuts.

"You could see the shock in the Republicans -- this is not what they were expecting from the White House," said Stan Collender, managing director of Qorvis Communications in Washington and a former staff member for the House and Senate budget committees. "There was almost euphoria among Democrats that the president was playing hardball."

The two parties are stalemated over where to cut spending and increase revenue to address a budget deficit that's exceeded $1 trillion for each of the four years Obama's been in office.

The administration says no agreement is possible unless Republicans agree to increase tax rates for the highest-earning Americans. Republicans oppose any tax-rate increase and demand deeper cuts than Obama has offered.

House Speaker John Boehner sent Obama a counterproposal Monday calling for $800 billion in unspecified new revenue over 10 years and cuts in programs such as Medicare and Medicaid.

Administration officials and congressional Republicans say they want a deal before year's end -- without either side publicly offering compromises.

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"There's not going to be an agreement without rates going up," Geithner said in a taped interview that aired Sunday on CNN's "State of the Union."

Republicans will "own the responsibility for the damage" if they "force higher rates on virtually all Americans because they're unwilling to let tax rates go up on 2 percent of Americans,"he said.