LONDON (Reuters) -- Britons are not convinced the war in Afghanistan can be won, Britain's chief of defense staff said as two new polls showed support for the war was dwindling.
"People remain to be convinced about whether or not this is doable," Jock Stirrup, told the BBC on November 8.
His comments came as the defense ministry announced the 231st British military death since fighting began in 2001, the eighth in the last week.
"We have not done a sufficiently good job in answering three basic questions," he said.
"Is it important enough to us as a country, to our security, to justify the price that our people are paying? ... is it physically doable? ... and are we doing it properly?"
Two polls published on Remembrance Sunday showed public support for the war has fallen, a blow to Prime Minister Gordon Brown who has this week sought to bolster backing at home to keep British troops in Afghanistan.
Continuing loss of British lives in Afghanistan could damage Brown's Labor Party in an election he must call by next June and which the opposition Conservatives are favorites to win.
A ComRes poll for the BBC found 64 percent of Britons now believe the war is "unwinnable", up from 58 percent in July, while two-fifths of people said they did not know why British forces were in Afghanistan.
More than half agreed that corruption in Afghanistan's government meant the war was "not worth fighting for".
Stirrup said the troops were not there to defend the Afghan government, reiterating Brown's comments earlier this week that British troops were there to protect Britain from terrorism.
"We are there to hold the security ring so that political solutions can be delivered, but we are only holding the security ring until the Afghans are capable of doing it themselves."
He said he thought the estimates of General Stanley McChrystal, commander of U.S. and NATO forces in Afghanistan, that the Afghan national army would be able to take over security by 2013 were "optimistic", and said 2014 was likely.
A YouGov poll for Sky news found that support for the war had dropped to 21 percent, from 28 percent in August, while 63 percent said British troops should not be in Afghanistan, up from 57 percent three months ago.