Barack Obama will almost certainly have to decide in the next few weeks whether to send more US troops to Afghanistan in order to defeat the Taliban. The decision is set to be one of the most difficult he has faced since becoming president. Back in the spring, just weeks after taking office, Mr Obama sent an additional 21,000 troops to Afghanistan, acknowledging the need to entrench security on the ground, and taking total American forces deployed to 68,000. However, the top US soldier in Afghanistan clearly believes this is not enough. General Stanley McChrystal, who took over as commander of the Nato mission in June, is likely to tell the president later this month that thousands more US troops are needed if the campaign is to be properly resourced and success achieved.

Gen McChrystal filed a report to the president this week on the deteriorating situation in Afghanistan, but did not say exactly how many extra troops he wants. But even the most modest request will be politically demanding. A growing number of Americans is becoming disenchanted with a war they believe impossible to win. The Taliban is a more effective opponent than the US had anticipated, quadrupling the number of successful attacks on Nato forces in the last two years. Allegations of fraud in the Afghan election make it unlikely that Washington will have a credible partner once a result is announced. Meanwhile, US and British fatalities mount. With four months of 2009 still to go, this is already the deadliest year for both nations since they entered Afghanistan in 2001.