A year after President Obama laid out new conditions for drone attacks around the world, US forces are failing to comply fully with the rules he set for them.

The rules are to strike only when there is an imminent threat to Americans and when there is virtually no danger of taking innocent lives.

A barrage of drone-fired missiles hit al-Qaeda cells in Yemen in mid-April and killed dozens of militants.

The results were strikingly different from a mistaken US attack on a Yemeni wedding convoy just four months earlier.
              
But even though the drones apparently found their targets this time, they were still blamed for a number of civilian deaths.
              
Mr Obama promised greater transparency in his speech at the National Defense University, US lawmakers are increasingly critical of the secrecy surrounding the operations.
              
Some drone hits have taken out militant leaders in places such as Yemen and Pakistan.

There are growing concerns in Washington that the net effect of the targeted-killing programme may be counterproductive.

"Collateral damage" is seen as an al-Qaeda recruiting tool that under cuts the main rationale for the drone campaign - to make Americans safer.
              
A former US national security official said: "It's never a good idea to make more enemies than you get rid of." 
              
In his speech on 23 May last year, Obama defended the drone programme as effective while promising to narrow its scope.

He is showing no sign of relinquishing what has become his counter terrorism weapon of choice since he took office in 2009.
              
Drones are spreading to new areas as US operations hone in on al-Qaeda affiliates in far-flung places like Somalia and in Nigeria.

American forces are helping the search for more than 200 girls kidnapped by the Islamist group Boko Haram.
             
Mr Obama's restrictions for drone attacks are having some impact.

Even with the recent surge of strikes in Yemen, the overall pace of attacks and the rate of civilian casualties have fallen appreciably.
              
There has even been an unofficial pause in attacks in Pakistan since the beginning of the year.

Pakistan made a request for restraint while it negotiated with the Taliban and a dwindling number of "high-value" targets in border areas.