In a long-anticipated speech on new strategy for Afghanistan, President Barack Obama said Tuesday that the U.S. army troops will withdraw from Afghanistan in July of 2011.

Speaking at the U.S. Military Academy in West Point, President Obama announced the deployment of 30,000 additional troops to Afghanistan and the acceleration of security responsibility transfer from U.S. forces to Afghans.

"As commander-in-chief, I have determined that it is in our vital national interest to send an additional 30,000 U.S. troops to Afghanistan. After 18 months, our troops will begin to come home," said Obama, who told his people "Afghanistan is not lost."

As to the decision to send additional troops, Obama said he made the decision because he is convinced that U.S. security is at stake in Afghanistan and Pakistan. "This is the epicenter of the violent extremism practiced by al-Qaeda."

The president also called on all U.S. allies, especially the North Atlantic Treaty Organization (NATO) , to offer their firm support for the U.S.-led mission in Afghanistan to successfully dismantle, disrupt and destroy the al-Qaeda network.

"Now, we must come together to end this war successfully. For what's at stake is not simply a test of NATO's credibility -- what's at stake is the security of our Allies, and the common security of the world," said Obama.

"Taken together, these additional American and international troops will allow us to accelerate handing over responsibility to Afghan forces, and allow us to begin the transfer of our forces out of Afghanistan in July of 2011," Obama said.

"Just as we have done in Iraq, we will execute this transition responsibly ... we will continue to advise and assist Afghanistan's Security Forces to ensure that they can succeed over the long haul. But it will be clear to the Afghan government -- and, more importantly, to the Afghan people -- that they will ultimately be responsible for their own country," said the president.

Obama had ordered to send 21,000 additional troops to Afghanistan in March and the U.S. troop level there has grown to 68,000. However, as the situation in Afghanistan deteriorates, Stanley McChrystal, the top U.S. commander in Afghanistan, has been calling for 40,000 more troops since August to quell the insurgency led by the Taliban.