Nato helicopter in Afghanistan
© Omar Sobhani/ReutersA Nato helicopter flies above the site of the bomb blast in Kabul.
Latest deaths of US troops in an apparent Kabul suicide attack come as support back home for the war reaches a new low

The latest deaths of 13 Americans in Afghanistan in an apparent suicide bomb attack in Kabul comes at a moment when the US public's attitude to the long war is at an all-time low.

A poll late last week, by CNN and ORC International, revealed that only 34% of Americans now support the war, one percentage point down on the previous all-time low. It found that 63% of Americans are now opposed to the war. The deaths of yet more Americans in a conflict that has already cost the lives of more than 1,700 American soldiers is only likely to see support fall further. Indeed the poll showed that some 58% of Americans say that the conflict is now similar to the Vietnam war.

The war is now a serious problem in Obama's strategy for the 2012 election. For a president who already faces discontent over accusations from the left of the Democratic party that he is too close to the Republicans, the Afghan war represents another area where he is out of step with many on his own side. The same poll showed that some six in ten Republicans still supporting the war, compared to just a quarter of Democrats.

Not that anyone thinks formulating strategy in Afghanistan is easy.

Obama's current plan is focused on a gradual drawdown of the extra 33,000 "surge" troops he sent after overhauling Afghan policy in 2009. Those troops are set to leave by the end of 2012. Last week the Pentagon revealed an assessment saying that goal was "on track" even as it also acknowledged that civilian casualties - mostly caused by the Taliban - had reached record numbers this summer with 450 dying in July alone.

Saturday's deaths fit the pattern of violence described in the latest Pentagon analysis, as they were caused by an isolated attack, not a mass assault. But that will be of little help to policymakers who must seek to show that the drawdown is taking place against an improving security situation, rather than a worsening one.

But playing a double game seems a central part of US strategy in Afghanistan. Hillary Clinton, the Secretary of State, last week testified to an increasingly restive Congress and reinforced the administration's strategy of pursuing a twin track policy of both talking and fighting with the Taliban and other militant groups. That particularly holds true with the so-called Haqqani group, which was responsible for a recent attack on the US embassy in Kabul.

American officials admit they have pursued talks with the group at the same time as urging Pakistan to increase military pressure on the organisation. Clinton told Congress: "We want to fight, talk and build all at the same time. Part of the reason for that is to test whether these organisations have any willingness to negotiate in good faith. There's evidence going both ways," Clinton said.

In that context Saturday's deaths in Kabul will make little difference to America's Afghan strategy on the ground. The US will continue its seemingly contradictory policy of seeking to withdraw extra troops - even as civilian casualties rise - while also fighting and talking with its enemies at the same time. It is impossible to say definitively how effective that strategy will be. But as pure politics it is perhaps unsurprising that Clinton's defence of the US role met with an increasingly sceptical Congressional reaction.

Nor have the actions of US allies helped. Last weekend Afghan president Hamid Karzai said that his country would back Pakistan if the US and its neighbour ever went to war. The statement was the latest in a series of Karzai remarks that have angered US officials, and they have not gone unnoticed by American politicians looking to score points against US policy. That includes senior Democrats as much as Republicans.

"Karzai's insult to America tells me that it's time for our country to stop pouring our limited taxpayer dollars and losing precious American lives in a country where we aren't even welcome - and even worse, where they have the gall to threaten to side against us," said Democrat Senator Joe Manchin. Clinton defended US policy robustly against that sort of argument in her testimony to Congress. But in the end it is likely that sort of political attitude - especially from within his own party - which is likely to shift Obama's strategic thinking more than any deaths on the ground.