By Carola Hoyos in Cairo

Delegates of the Opec oil cartel yesterday began to arrive for their emergency policy meeting in Cairo, just as American families criss-crossed the US to reunite for their Thanksgiving dinners. The two gatherings may appear worlds apart, but in fact they are closely linked. The US accounts for almost a quarter of the world’s oil demand, lapping up nearly one in every five barrels of the oil Opec produces.

For Opec ministers ahead of Saturday’s meeting, the number of trips by US drivers will be key in measuring the health of oil demand as they consider a production cut to shore up oil prices that have tumbled from July’s record of almost $150 a barrel to yesterday’s $52.85.

The US recession has prompted oil demand to plummet, reflected by the number of Americans - 1.2m of whom this year have lost their jobs and daily commutes - unable to afford to travel this Thanksgiving. The day, together with Labor Day, is the US’s most heavily travelled holiday. So many people take to the skies that the White House has to open up military airspace to ease congestion.

But this Thanksgiving the American Automobile Association predicts fewer people than last year will travel more than 50 miles, marking the first drop since 2002 when the US economy was struggling and Americans had just marked the anniversary of the terrorist attacks of September 11, 2001.

The American Transport Authority, the industry group, expects a 10 percent drop in passengers travelling on US airlines this Thanksgiving. Inland deliveries of oil products - a proxy of oil product demand - contracted by 8.5 percent in October, the most recent month for which data is available, compared with the previous year. SUV and light truck sales plunged by more than 30 percent and the US Department of Energy expects petrol demand this year to mark its steepest decline since 1980.

Demand continues to fall even though petrol prices have tumbled, taking US petrol pump prices from $4 a gallon to less than $2.

Joseph Stanislaw, an industry consultant, said: “We’ve gotten a Thanksgiving gift. Gasoline prices are at $1.85 a gallon. But Americans would rather have their jobs.” Opec would also prefer a strong US economy because oil prices and economic prosperity are closely correlated. The downturn in the US economy, which has spread to the rest of the world, has hit the cartel hard with the price of its oil falling below the threshold $50 that all but three of Opec’s members need to balance their budgets in 2009, according to PFC Energy, the industry consultants.

Chakib Khelil, Algeria’s energy minister and Opec’s president, said we are “very concerned about the economic situation which has worsened in the US and Europe, which has entered recession, followed by Japan”.

The cartel has already announced output reductions of as many as 1.8m barrels a day and its most hawkish members, including Venezuela and Iran, are calling for those cuts to be deepened when they meet on Saturday.

Nansen Saleri, a former senior official at Saudi Aramco, the kingdom’s national oil company, said: “Saudi Arabia sees itself as the reliable anchor of global oil supplies. This is pre-eminent in their thinking. But they have to balance that with their budgetary needs.”

For Saudi Arabia, Opec’s biggest and most influential member, its relationship with the US is particularly important, not least because the kingdom has much at stake in two of President-elect Barack Obama’s key policy areas: Middle East foreign relations, particularly in regards to Iran and Iraq; and Obama’s ambition to reduce radically America’s dependence on oil.