Crowds gathered across the nation as Victoria Cross recipient Corporal Ben Roberts-Smith recited letters from his mates, both fallen and fighting, in a moving tribute to Diggers on Anzac day.

ONE of the world's most powerful military commanders has ranked Australian special forces soldiers as among the best he has seen and wants them to play an increasing role in global security.

Supreme Allied Commander of NATO forces Europe, US Admiral James Stavridis, said Australia was now in the top tier of alliance partners and its niche military capabilities served as a model for future operations.

But in a frank assessment of how the world would handle new and emerging threats, he said security in the 21st century could not be delivered simply "down the barrel of a gun".

He also raised concerns about the future of Afghanistan after our troops withdraw next year, claiming insurgent sanctuaries in Pakistan, corruption and an illegal drug trade funding the Taliban would be major challenges.

As tens of thousands of Australians attended services here and around the world to celebrate the service of their countrymen in past and current wars on Anzac Day, Admiral Stavridis was interviewed by News Ltd at NATO headquarters in Brussels. Meanwhile, foreign ministers including Bob Carr and US Secretary of State John Kerry gathered to discuss the future of Afghanistan and the long-lasting crisis in Syria.

Anzac Day: How Australia remembered here and around the world

Admiral Stavridis, who commands the world's largest military force through the US/Europe alliance, said Australia - a non-NATO contributor in Afghanistan - would become a key military partner for NATO as it expanded its influence beyond its traditional World War II boundaries.

Suggesting global security threats would have to be managed differently from conflicts of the past, he cited Australian capabilities as a model for the transition to reconstruction in Afghanistan.

"Can I start by saying thank you Australia for your contribution," he said.

"When I look at the specifics of what Australia has done in Afghanistan, it really is quite extraordinary, it goes from difficult challenging combat roles in Uruzgan, to training and advising. It is the model for the rest of the transition.

"Some of the areas I think Australia is very strong in are special operations.

"You have one of the top forces in the world.

"And the training and mentoring in Uruzgan was particularly valuable."

Admiral Stavridis, who will end his NATO command in May, said the role of the military in future global security threats would change.

"At the end of the day we are not going to delivery security in the 21st century from the barrel of a gun ... there are going to be times when we need our guns no doubt about it....but we have to have this holistic approach," he said.

"It includes diplomacy, development, public private partnerships, inter agency work, and the military as a security component."

Beyond Afghanistan, he believed that Australia had a growing role in maintaining global security, suggesting NATO would seek closer engagement with this country.

"If you look at where NATO is operating around the world...we are on three continents.....there is a necessity for the alliance to be larger than its originally constrained area of the North Atlantic."

On the 12 year war in Afghanistan, Admiral Stavridis said while he believed the mission would be successful there were lessons to be learnt.

"I am cautiously optimistic that we will succeed in Afghanistan," he said.

"It's the success we are seeing so far of the transition to Afghan security operations...today as we sit here almost 90 per cent of the country is under Afghan security.

"When I look back four years ago to when I started, I could not have imagined that level of transition success.

He also cited the improved literacy rates among children and access to health as key successes of the overall mission.

"(but) the challenges are very real and they include a very difficult relationship with Pakistan.

"In Pakistan we have sanctuaries of insurgents who can get across the somewhat porous borders...so that relationship is challenging,, "There continues to be corruption...that is something we are all struggling to help our Afghan partners overcome...that will be a long term challenge in Afghanistan.

"The other problem is narcotics...both the volume and the insidious quality of the trade in narcotics provides funding back to the Taliban."