London, Sep 19 (DPA) British Defence Secretary Des Browne admitted Tuesday that NATO's mission in Afghanistan had turned out to be "even harder than expected" and that the scale of the task had been underestimated.

Speaking in London, Browne said: "We always knew the south (of Afghanistan) would be hard. We do have to accept that it's been even harder than we expected. The Taliban's tenacity in the face of massive losses has been more than we expected."

According to Browne, there is a "hard core" of about 1,000 Taliban who were "implacable, irreconcilable and determined to keep their impunity in the south and possibly reclaim control of the whole country."

Forty British soldiers have died in Afghanistan since 2001, but most of the fatalities were recorded in the last four months.

Browne, who was speaking to military experts at the Royal United Services Institute in London, said there had been "very little progress in governance and reconstruction" in south Afghanistan.