A week after President Barack Obama cracked the lid of secrecy on his drone war, the United States refused Wednesday to confirm it had killed a top Pakistani Taliban leader in an airborne attack.

Pakistani security and intelligence sources said that Waliur Rehman, deputy leader of the Tehreek-e-Taliban Pakistan (TTP) had perished in an American drone strike, along with at least five other people, in North Waziristan.

But senior officials in Washington stuck to their normal practice of declining to provide details of US operations, and only hinted that Rehman, wanted for attacks on Americans and Pakistanis, had been killed.

The attack appeared to be the first known US drone strike since Obama's speech last week laying out new criteria for the covert use of unmanned aerial vehicles in strikes against terror suspects and militants.

"We are not in a position to confirm the reports of Waliur Rehman's death," White House spokesman Jay Carney said.

"If those reports were true, or prove to be true, it's worth noting that his demise would deprive the TTP of its second-in-command and chief military strategist," Carney said.

Rehman is also wanted in connection with attacks on US and NATO personnel across the Afghan border and for involvement in the attack on American citizens in Khost, Afghanistan on December 30, 2009.

That strike, though Carney did not describe it in detail, was a dark day in CIA history, when seven counter-terrorism agents and security contractors were killed in a suicide bombing inside a US base.

Carney would not confirm whether the attack on Rehman satisfied the new criteria for drone strikes established by Obama last week during a speech that aimed to recast the country's decade-long battle against terrorism.

In the speech, Obama said lethal force would only be used to "prevent or stop attacks against US persons," when capture is not feasible and if a target poses a "continuing, imminent threat" to Americans.

Carney pointed to a clause in Obama's remarks in which he said that in the "Afghan war theater" Washington must support its troops until the NATO withdrawal is complete in 2014.

He appeared to be making a case that Rehman's killing may have satisfied the new guidelines because he may have posed a direct and imminent threat to US troops across the border in Afghanistan.

The president said in his speech that strikes would continue against "high value Al-Qaeda targets, but also against forces that are massing to support attacks on coalition forces."

A CIA spokesman also declined to confirm Rehman's death.

Carney dismissed the idea that keeping reporters in the dark about the reported attack conflicted with Obama's pledge for more transparency over the drone war. He said the speech at the National Defense University last week contained an "extraordinary amount of information."

"It does not mean that we are going to discuss specific counter-terror operations," Carney said.

Security, tribal and intelligence officials told AFP in Pakistan that Rehman, who had a $5 million US government bounty on his head, was the target of the strike and was killed.

Pakistani security officials said the others killed in the attack were TTP cadres, including two local-level commanders. There were no initial reports of civilian casualties.

According to Britain's Bureau of Investigative Journalism, CIA drone attacks targeting suspected Al-Qaeda and Taliban militants in Pakistan have killed up to 3,587 people since 2004, including as many as 884 civilians.

The frequency of drone strikes in Pakistan has tailed off in recent months, with the previous one coming on April 17.