The UK's front-foot approach has led to more casualties, says Brig Messenger
The British military is stretched and the recent rise in casualties could continue, the commander of British forces in Afghanistan has told the BBC.
Brig Gordon Messenger said the enemy was dangerous and committed and insurgency increasingly sophisticated.
The outgoing head of Task Force Helmand also welcomed the deployment of 8,000 extra US troops to the province and said he hoped it would speed progress.
The UK now provides security to 60% of Helmand, he added.
"We have been running a campaign of a similar size in Iraq, and one here, and the armed forces are stretched as a result," he said.
"So of course there's a limit to what we can put in. I think every nation would say there's a limit to what military and other resources they can commit."
He said the increase in the rate of casualties was a result of "taking a front-foot approach" and there were no guarantees it would end.
"I think there will be more casualties in this campaign," he said.
"I hope the rate we've experienced won't be experienced by others, but this is a dangerous campaign, we are up against a committed enemy force, and they are out to kill and injure us."
Brig Messenger said there had been successes on and off the battlefield but warned the tactics of the insurgents were evolving to match those of the coalition.
He also admitted a tipping point against the Taleban had not yet been reached.
The US is deploying up to 8,000 extra troops and more resources to Helmand this summer, and that is expected to change the military campaign significantly.
Brig Messenger said he hoped for "an upsurge in the pace of progress" when American forces arrived, and described Helmand as "the biggest problem in the country" in terms of security.
He also confirmed the new forces would not answer to his command and paid tribute to those who have been killed or injured.
The head of British forces in Afghanistan personally writes to the families of all UK troops killed there.