Aides to the president - who Saturday called the US$787-billion (S$1.19 trillion) package of investment and tax cuts 'a major milestone on our road to recovery' - said he would outline his housing plan in Phoenix, Arizona on Wednesday.

The day before, in Denver, Colorado, Mr Obama will sign the stimulus package into law, setting the seal on the first major legislative triumph of his young presidency.

'I think it's safe to say that things have not yet bottomed out,' White House spokesman Robert Gibbs told CNN on Sunday.

But US states will start getting the stimulus money 'relatively quickly,' he said, 'so they don't have to lay off police officers or firefighters or teachers' and can begin to create jobs in alternative energy.

Meanwhile Mr Gibbs, underlining that Mr Obama will have signed an ambitious economic bill within just four weeks of taking office, denied that the president's promise of bipartisanship had taken a hit.

'He's going to continue to reach out to Republicans, and he's hopeful that Republicans will start to reach back,' he said on CBS television.

But Republicans, chafing already at the largest package of government spending in US history, signalled more fights ahead as Obama prepared to take on the stricken housing and financial markets.

Senator Lindsey Graham cited estimates that half a trillion dollars could be needed to fix the property sector, whose tailspin from boom to bust has crippled much of Wall Street and ignited the broader economic crisis.

After the first round of a banking bailout and now the stimulus bill, 'it makes it harder for everybody here to go back to the public and say, 'Please give us more money, because we seem irresponsible',' he said on ABC News.

Senator John McCain, Obama's vanquished rival for the presidency, said on CNN: 'These are the worst, most difficult challenges, foreign and domestic, perhaps we have faced certainly in our lifetimes.

'So let's start over now and sit down together.' However, senior Obama adviser David Axelrod said Republican complaints smacked of hypocrisy.

'For eight years when we were doubling the national debt, I didn't hear many of these people moralizing about spending,' he said on NBC, noting that barely any Republicans opposed former president George W. Bush's Iraq war expenditure. -- AFP