As troops leave Afghanistan defence experts tell Channel 4 News securing the violent eastern border with Pakistan will become a priority, and that may include the use of more unmanned drone strikes.

Drone strikes 'may increase' after withdrawal (Reuters)

After President Obama's announcement that 10,000 US troops will begin to exit Afghanistan by the end of the year, there have been indications that America could intensify its controversial use of unmanned drones in the region around the Afghan-Pakistan border.

Over the last year the US focus has been in southern Afghanistan, with 38, 500 troops in that region. This compares to 31, 000 troops in the east of the country. Forces in the east have suffered far higher casualties from a cross-border flow of Taliban and Haqqani network fighters.

Last week US Army Lt Gen David Rodriguez, Nato's second-ranking commander in Afghanistan said that in the east "we really haven't focused our energy and efforts, because you can't do it everywhere at the same time."

Bill Roggio, the editor of The Long War Journal, a US publication analysing the global war on terror, told Channel 4 News that he expects "counter-terrorism on both sides of the border to pick up significantly in the absence of ground troops."

"If the military had its wish it would have taken more forces into the east, but that is obviously not going to happen now. So they'll use air assets as they have said the east is a priority," Mr Roggio said.

More from Channel 4 News: 'Hit and run' drone strikes are 'breaking laws of war'

Although there has been no official announcement on the use of air assets in Afghanistan, and the covert use of air strikes in Pakistan, senior research fellow for air power and technology at the defence think-tank Rusi, Elizabeth Quintana, told Channel 4 News a "surge" in drone strikes to kill suspected militants along the border is a possibility.

"Generally speaking if you look at drawdown in Iraq, the use of air power has not decreased, but it has certainly been used to maintain air superiority, I expect the same thing to happen in Afghanistan," Ms Quintana said.

She added that drone strikes could increase when General Petraeus, the current Nato commander in Afghanistan, moves to head the CIA later in the year, considering the CIA is believed to be operating unmanned drones in Pakistan.

The legality of drone strikes
Pakistani lawyer Shahzad Akbar, who is representing 50 families of civilians who have died in drone attacks, tells Channel 4 News that the US attacks on Pakistani soil are 'simple homicide.'

The CIA has not idea who actually is being targeted and the term militant/terrorist is being used very loosely.

Our stance is in absence of any valid legal justification it is plain and simple homicide. Presence of militants in any area of Pakistan is responsibility of Pakistani State, and US or UN/Nato should liaise with Pakistan in curbing out such elements within confines of law and due process.

One foreign state taking suck target killing actions against another sovereign state is a bad precedent. It would also give justification to nuclear armed India to drone militant camps in Kashmir and give birth to a nuclear armed conflict in the region.

"If you look at General Petraeus' counter-insurgency strategy, it is very much about using air power as an asymmetrical edge over insurgents," Ms Quintana said.

"When you consider he is taking over the CIA, it is likely that drone strikes in east Afghanistan and Pakistan won't decrease," she continued.

However, General Petraeus has told the US Senate that he has no plans to bring "my military brain with me," when he takes up his new role.

That's despite Petraeus' existing close ties with the CIA, when he organised so-called "fusion cells" with the agency to strike at al-Qaeda and Taliban leaders in both Afghanistan and Iraq.

Speaking at the hearing to confirm his nomination as the new CIA Director, Petraeus said the CIA would be "relentless" in pursuing intelligence needed by the government.