President Obama announced Tuesday night that he will reinforce Afghanistan with some 30,000 more United States troops to reverse the momentum of the Taliban insurgents, and begin to withdraw in July, 2011.

The 30,000 additional troops that I am announcing tonight will deploy in the first part of 2010 - the fastest pace possible - so that they can target the insurgency and secure key population centers the President said in a speech at US Military Academy, West Point.

The decision, coming some 90 days after Afghanistan General Stanley McChrystal requested more troops, is seen to be a pivotal decision of the Obama presidency. Obama is hoping that the influx of troops, can turn around the eight-year war.

Additional troops are expected to bolster the US's ability to train Afghan Security Forces, and to partner with them so that more Afghans can get into the fight, Obama said, adding that they will help create the conditions for the United States to transfer responsibility to the Afghans.

The move will bring the total American troop involvement to nearly 100,000 by the end of May, moving more quickly than the administration had originally planned. It follows his previous decision to increase forces by 21,000 earlier this year

The President is also pressing its allies in NATO and elsewhere in the world to commit to increasing their deployments to Afghanistan.

There are about a further 40,000 NATO and allied troops in Afghanistan which the US including 500 already pledged by the UK and up to 1,000 from Georgia. The UK currently has 9,500 deployed.

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.

According White House's calculations, the new deployment could cost the US government $30 billion a year, in addition to the cost of maintaining existing troops.

Republicans expressed support for the size and the speed of the deployment on Tuesday. But they voiced concerns about setting a date for a drawdown.