Despite threats of retaliation from Pakistani militants, senior Obama administration officials said Monday that the United States intended to step up its use of drones to strike militants in Pakistan's tribal areas and might extend them to a different sanctuary deeper inside the country.

On Sunday, a senior Taliban leader vowed to unleash two suicide attacks a week like one on Saturday near Pakistan's capital, Islamabad, unless the CIA stopped firing missiles.

But as Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, and Richard Holbrooke, the U.S. special envoy to the region, arrived in Islamabad on Monday, the administration officials said the plan to intensify missile strikes underscored President Obama's goal to "disrupt, dismantle and defeat" Al-Qaida in Pakistan and Afghanistan, as well as allied militant groups. Officials are also proposing to broaden the missile strikes to Baluchistan, south of the tribal areas.


German Chancellor Angela Merkel made an unannounced visit to northern Afghanistan on Monday to meet with some of the 3,800 German troops there and view rebuilding efforts. Meanwhile, an insurgent rocket hit the Netherlands' main base in southern Afghanistan, killing a Dutch soldier.