Should war in Iraq finally begin, a recovery of the world economy is likely to hinge on how long it lasts.
The start of a long-awaited US-led attack, economists reckon, will probably give financial markets a lift by removing the months of uncertainty associated with the build-up of tension in the Gulf.
But a sustained boost to world economic activity is only likely if a long and messy military campaign can be avoided and the market relief proves to be more than a temporary filip.
The extent of economic impact will also depend on a host of unknowable variables - particularly whether there is oil field damage, an urban battle in Baghdad or use of weapons of mass destruction.
One thing is certain: the world economy would be starting this war from a weaker position than most expected even just a few months ago.
International Monetary Fund head Horst Koehler has forecast a global expansion of just above three per cent this year, down from 3.7 per cent growth foreseen last September. But a protracted war could shave as much as two percentage points off that forecast.
Former US Federal Reserve Governor Laurence Meyer believes the start of the war would lift uncertainties hurting consumer and business spending. But without a clear resolution to the crisis, those unanswered questions will continue to dog the economy.
Mr Meyer, now at the Centre for Strategic and International Studies, sees the best case as a swift victory, which he thinks would boost stocks and consumer confidence and add a half percentage point to US growth this year.
He ascribed a 40 to 60 per cent likelihood to a war of less than six weeks. He gives a 30 to 40 per cent probability of the war lasting as long as three months, which he says would knock 1.75 percentage points off US output this year.
The worst-case scenario, with a five to 10 per cent likelihood, is a war of up to six months with urban battles, oil facilities burning, regional disruption and terror attacks in the United States and Britain. Mr Meyer said that would knock 4.5 percentage points off US economic growth.
"The economy grows more slowly in the no-war case and in the intermediate case and the US and global economies are thrown into recessions in the worst case-scenario," he said.
Conservative calculations of the cost of the war for the United States, which assume a swift campaign along the lines of the 1991 Gulf war, come in at around $100 billion, equivalent to one per cent of US economic output.
Most economists are betting on a short war with a speedy US victory. That, they said, will lift the uncertainty, push the price of oil back to about $25 a barrel from prewar levels of close to $40 and set stock markets rallying.
A brief war could spur US growth to a pace as fast as five per cent by year-end with the global economy clocking a three per cent expansion rate, many private economists expect.