In his first statement to MPs since taking on the new role Philip Hammond said UK troops in Helmand province were having a "tangible impact" on insurgent activity.
The group is reportedly considering options such as a gradual pull-out of American troops and a diplomatic push to persuade Iran and Syria to curb the insurgent groups they are thought to encourage.
But optimists note that perhaps a hundred are now seen as ready to some degree, and Iraqi troops took a leading role in a recent offensive in Tel Afar, an insurgent stronghold.
He said security in Helmand was improving, with Afghan forces now responsible for the bulk of the province - but that the environment in which UK troops operated remained "risky and dangerous including the threat of improvised explosive devices and insurgent attack".
While agreeing that there had been progress, Mr Brown said that "gains have been overshadowed by recent events" including some allies setting unilateral withdrawal dates for their troops, a deterioration in relations between the United States and Pakistan, and continuing insurgent attacks.