Declaring that "our cause could not be more just," President Obama today formally announced a new strategy for Afghanistan and Pakistan that will require more U.S. spending, more troops and a renewed commitment from Americans and their allies to a flagging war effort.

Obama told an audience of foreign diplomats and U.S. officials that, while "there will be difficult days ahead," the United States and its allies must step up efforts against Al Qaeda militants who have taken haven in Pakistan's border regions and are even now "actively planning attacks" on America.

Pakistan's western border region "is now the most dangerous place in the world" for Americans, he said.

Obama outlined a plan, developed during a two-month review, that will add 4,000 U.S. troops to train Afghan security forces and will step up U.S. spending on civilian efforts to help both Afghanistan and Pakistan. The United States' spending for civilian efforts in Pakistan alone will amount to an additional $1.5 billion a year.

Obama said the new approach would be a "comprehensive" effort that would replace what he portrayed as a fragmented, poorly coordinated approach from the Bush administration. But while Obama sought to distance the new plan from that of his predecessor, he sounded like Bush as he painted the security threat in dark tones.

He said that the security threat from the militants represented an international security challenge "of the highest order."

He said his message to the "terrorists ... is the same: We will defeat you."

With restless members of his Democratic Party clearly in mind, Obama said that the United States will not "write a blank check" to the Pakistani government, but will lay out "benchmarks" for progress that Pakistan must meet.

He acknowledged the difficulty of asking for more U.S. spending at a time of economic crisis at home.

"I don't ask for this support lightly," he said. "The American people must understand that this is a down payment on our own future."

While Obama has spoken of the need for an "exit strategy" that will gradually put more of the burden of the fight on the Afghan government, it also was clear that the U.S.-led commitment will last for several more years. U.S. military officials have said they expect a large international effort in Afghanistan to last for at least three more years.

Obama called for a renewed commitment from NATO allies, several of whom are planning to begin reducing their troop levels in Afghanistan later this year. The administration hopes the Western allies will be willing to step up their efforts to help strengthen governance and social stability in Afghanistan.

He also signaled that he wants a new commitment to the effort from regional powers, including Central Asian nations, Russia and China. He said India, too, needs to be drawn into the international effort.

paul.richter@latimes.com