The number of Taliban attacks in Afghanistan has declined for the first time in a "welcome" trend in the ten-year-old war, an officer with the NATO-led force said Tuesday.

Overall insurgent attacks are down in the past two months compared to last year and the Taliban has failed in recent months to seize back territory lost in US-led offensives in the south, said Major General Michael Krause, an Australian officer who serves as deputy chief of staff for International Security Assistance Force (ISAF).

"Every year there have been more violent activities in Afghanistan since the previous year except this one," said Krause by video link from Afghanistan.

"Over the last two months the violence trends in Afghanistan have reduced compared with last year ...," he said.

ISAF statistics showed insurgent assaults were down in 17 of the last 22 weeks, he said.

"Now, that's a trend. And although we still face tremendous challenges and we always must remain realistic about our objectives and goals, that's a very, very welcome trend and the first year that we've seen that trend," said Krause, on his second tour in Afghanistan.

But despite the upbeat assessment, the course of the war remains the subject of debate amid doubts about Afghan security forces and the corruption-plagued Afghan government.

ISAF's account also differed from a United Nations report last month showing the total number of security incidents up 39 percent in the first eight months of 2011, compared to the previous year.

Krause said the discrepancy between the ISAF and UN tallies could be explained by a difference in how the two organizations calculate violence trends.

The UN counts all security-related incidents, including reported threats and street demonstrations, while the NATO-led coalition only tallies confirmed violent attacks, he said.

Recent high-profile attacks by the insurgency, including a 19-hour-long assault on the US embassy in Kabul and a truck bombing that wounded 77 American troops, had obscured broader progress in the war effort with NATO now seizing the momentum, he said.

But he said insurgent attacks have not declined in the east, where NATO-led forces have encountered a resilient adversary in the rugged mountains neighboring Pakistan.

The Australian general referred to trends but did not outline the total number of insurgent attacks this year or in 2010.

The Taliban had vowed to take back former strongholds in the southern provinces of Helmand and Kandahar but the summer fighting season came and went without the insurgency gaining back ground, Krause said.

"We still hold all of those population centers, and we've done so since we secured them. The Taliban has not been successful, and his offensive has failed," he said.

The Taliban acknowledged the battlefield setbacks in a communication intercepted by foreign forces, Krause added.

"He also knows he's failed. How do I know that?"

"Well, we intercepted a very, very welcome transmission from the inner shura not so long ago that admitted that Al-Badr (offensive) had failed. In fact, the translation used the phrase: utterly failed." he said.