US President Barack Obama called for a pre-Christmas deal with Republicans to avert a year-end tax and deficit crunch, as pressure mounted from the business world and stock markets fluttered. US lawmakers demanded urgent action to keep America from tumbling off the so-called \"fiscal cliff,\" and Treasury Secretary Timothy Geithner was to drive the point home Thursday when he meets members of Congress to discuss \"a balanced approach to reduce our deficit,\" his office said. Consensus has swelled that a deal -- either a full-blown grand bargain or part one of a multi-stage agreement -- ought to be reached before tax rates rise for millions of American families and deep spending cuts bite on the first day of 2013. Economists have said the $500-billion amalgam of tax hikes and spending cuts required by last year\'s debt-ceiling deal could pitch the US economy back towards recession next year. The president gathered middle class families at the White House to dramatize and boost his campaign for Republicans to join Democrats in Congress to pass an extension to tax cuts for most Americans, while bowing to his pressure to raise rates on top earners.\"I want to make sure everybody understands this debate is not just about numbers. It\'s a set of major decisions that are going to affect millions of families all across this country in very significant ways,\" Obama said. \"Our ultimate goal is an agreement that gets our long-term deficit under control in a way that is fair and balanced,\" he said. \"My hope is to get this done before Christmas.\" The president sought the public\'s help, urging Americans to use the Twitter hashtag #my2k to tweet our their support -- a reference to the $2,000-plus in additional taxes that the White House estimates the typical American family will have to pay if no deal is reached. But in a fit of social media warfare, The Heritage Foundation snagged coveted Twitter space by purchasing a \"promoted tweet\" for \"my2k,\" meaning anyone who searches for that hashtag sees the conservative thinktank\'s ad about why it\'s wrong to raise taxes. Obama, fresh from re-election, met with the Democratic and Republican leaders of the House and Senate earlier this month and expressed optimism that an agreement could be reached, with Republicans acknowledging they were willing to put the issue of revenue on the table. That optimism has appeared to fray, however, and the uncertainty led markets to sink in Asia on Wednesday, then close mixed in Europe.US stocks dropped on Tuesday and fell again at the opening bell Wednesday with traders fretting over a fiscal resolution, but US markets rebounded to close in positive territory. Democrat Nancy Pelosi, the House minority leader, was blunt about the need to negotiate. \"There has to be a deal,\" she said. \"I believe everybody knows what the possibilities are, so let\'s just do it.\" But Republican House Speaker John Boehner signaled no wavering in the taxes standoff, even after fellow Republican Tom Cole pitched taking the Democratic deal to prevent taxes from rising on the middle class while suggesting rates for the wealthiest be worked out later. Cole had argued that extending the Bush-era tax cuts for all families making less than $250,000 per year would give Republicans leverage in their bid to extend the tax cuts to the wealthy, as Democrats will still need to negotiate with Republicans on raising the debt ceiling by February. \"I told Tom... that I disagreed with him,\" Boehner said. \"You\'re not going to grow the economy if you raise tax rates on the top two (percent). It\'ll hurt small businesses, it\'ll hurt our economy.\" Defections from the party\'s \"no tax increase\" ideology have begun. They include Senators Lindsey Graham and Saxby Chambliss, who say they are willing to look toward raising taxes on the wealthiest if need be. Among those pressing for a resolution are US business leaders, 13 of whom met with Obama at the White House. \"I would like to not have a crisis that will wreck the economy and derail the recovery,\" Lloyd Blankfein, chief executive of Goldman Sachs Group, told CNN. Some experts involved in seeking a way out openly worried Wednesday about failure. \"I think the probability is we\'re going over the cliff,\" said Erskine Bowles, a former co-chair of Obama\'s debt commission, who has long sought a compromise on the fiscal challenges. He told reporters he believes \"chances are one-third that we\'ll get something done in the lame-duck\" session of Congress, with another one-third chance \"that we\'ll go over the cliff and people will come to their senses very quickly\" to forge a compromise. The final third of the chance was that no deal would be reached, an outcome Bowles called \"insane.\" Bowles met with Obama on Tuesday, and the president showed \"some flexibility\" on raising tax rates on the wealthiest, Bowles said, but \"the White House really believes at its core that revenue ought to come from the wealthy.\"