At Bangkok meeting, they cheer support for needle exchanges but urge further steps toward 'harm reduction.'
The opium trade helps fund the insurgency but also provides farmers livelihood.
The West African nation's status as a drug-trafficking hub has led to allegations of political corruption ahead of Sunday's presidential vote.
Secretary of State Condoleezza Rice suspended a trade deal with Bolivia last week for failure to rein in coca growing. Some 50,000 jobs could be lost.
Thomas Schweich charges that President Karzai is protecting drug traffickers within his power base, and says the US Defense Department and some NATO allies have also resisted antiopium efforts.
It faces one of the world's fastest rising rates of drug use.
In 2003, a violent government antidrug campaign resulted in more than 2,500 deaths.