Islamabad, Apr. 3 : Pak-Taliban chief Baitullah Mehsud is being seen as a growing threat to President Barack Obama's anti-terror strategies in Pakistan and beyond, experts say.

A day after Mehsud threatened to attack the White House, a US drone fired two missiles at the alleged hideout of one of his commanders, killing 14 people.

For years, the US had considered Mehsud a lesser threat than some of the other Pakistani Taliban, their Afghan counterparts and Al Qaeda, as most of his attacks were focused inside Pakistan, not against the US or NATO troops in Afghanistan.

US fears that Mehsud's growing powers could result in increasing violence in Pakistan, and destabilizing the nuclear-armed ally.

"Mehsud poses a very real threat to stability and security in Pakistan and Afghanistan," the Daily Times quoted Eric Rosenbach, a terrorism expert at Harvard's Kennedy School, as saying.

"He normally doesn't issue hollow threats," Brigadier (r) Mehmood Shah, a former chief of security in northwest Pakistan, told Reuters.

Mehsud, who is in his 30s, has said that his group was responsible for the attack on a police academy in Lahore, in retaliation for drone strikes.

He has no record of attacking targets abroad, although he is suspected of being behind a 10-man cell arrested in Barcelona in January 2008 for plotting suicide attacks in Spain.

He also threatened Washington in a flurry of phone calls to various media outlets.

Head of US Central Command General David Petraeus said that officials were studying whether Mehsud's warning posed a credible threat to the US.

"Everyone is quite riveted on analyzing that and seeing what further we can find out," Petraeus said in testimony before the Senate Armed Services Committee. (ANI)