In an address to the American Enterprise Institute at the Mayflower Hotel in Washington, Bush also called his strategy of a troop surge to secure Baghdad essential for success in Iraq.
"We have extended the stay of 3,200 troops now in the country for four months and we will deploy a replacement force that will sustain this increase for the foreseeable future," Bush said. "The forces and funds are going to help President [Hamid] Karzai defeat common enemies."
The boost in troop levels comes as Bush said the enemy "struck back with a vengeance" in Afghanistan in 2006.
'Fill In The Security Gaps'
But the U.S. president also said "remarkable progress" has been achieved in Afghanistan.
And he announced he is asking Congress for $11.8 billion in aid for the country over the next two years.
Calling Afghanistan NATO's most important operation, Bush called on alliance partners to "make sure that we fill the security gaps" there.
"In other words, when there is a need, when our commanders on the ground say to our respective countries we need additional help, our NATO countries must provide it in order to be successful in this mission," Bush said. "As well, allies must lift restrictions on the forces they do provide so NATO commanders have the flexibility they need to defeat the enemy wherever the enemy may make its stand."
Turning to Iraq, Bush called his strategy of a troop surge to secure Baghdad essential for success there.
"So far, coordination between Iraqi and coalition forces has been good," he said. "They are beginning joint operations to secure the city by chasing down the terrorists and insurgents and the criminals and the roaming death squads. They are doing what the Iraqi people want in Baghdad."
Giving The Troops What They Need
He also said both political parties in the United States -- his own Republican Party and the opposition Democrats -- have a responsibility to give U.S. troops in Iraq the resources they need:
"Now, the House [of Representatives] is debating a resolution that disapproves of our new strategy," Bush said. "This may become the first time in the history of the United States Congress that it has voted to send a new commander into battle and then voted to oppose his plan that is necessary to succeed in that battle."
The new commander is General David Petraeus, who was recently confirmed by the U.S. Senate to lead U.S. forces in Iraq.
Bush said that if the United States were to leave Iraq before the job is done "the enemy would follow us home."
A U.S. military vehicle damaged by insurgents near Kandahar (epa)
HOMEGROWN OR IMPORTED? As attacks against Afghan and international forces continue relentlessly, RFE/RL hosted a briefing to discuss the nature of the Afghan insurgency. The discussion featured Marvin Weinbaum, professor emeritus of political science at the University of Illinois at Urbana-Champaign, and RFE/RL Afghanistan analyst Amin Tarzi.
Listen to the entire briefing (about 83 minutes):Real Audio Windows Media
RFE/RL's coverage of Afghanistan
For weekly news and analysis on Afghanistan by e-mail, subscribe to "RFE/RL Afghanistan Report."