Mr. Obama unveiled his new strategy Friday, calling the situation "increasingly perilous" with insurgents controlling parts of both countries. Attacks against foreign troops and the Afghan government are also on the rise.
As part of the plan, 4,000 additional U.S troops will be sent to Afghanistan to train Afghan armed forces, on top of the 17,000 new troops to be deployed in the next months.
The president also called on Congress to authorize $1.5 billion in direct support to the Pakistani people every year over the next five years, to improve infrastructure and strengthen Pakistan's democracy.
Officials from both the Afghan and Pakistani governments welcomed President Obama's new strategy to stabilize their countries.
A spokesman for Afghan President Hamid Karzai says Afghanistan appreciates the recognition by the U.S. president that the threat from al-Qaida comes mainly from its neighbor, Pakistan. President Karzai is expected to hold a news conference on Saturday.
Pakistani Prime Minister Yousuf Gilani said Pakistani territory will not be allowed to be used for terrorist activities, which he said are carried out by a "minority of extremists." President Asif Ali Zardari welcomed Mr. Obama's initiatives to strengthen democracy in his country.
U.S. Defense Secretary Robert Gates told reporters the "comprehensive" strategy has a greater likelihood of success.
The European Union, United Nations, and members of the U.S. Congress also hailed President Obama's plan.
During a conference in Moscow Friday, Russia and its Asian neighbors pledged to play a stronger role in stabilizing Afghanistan.
Britain said Friday it was ready to dispatch more troops.
The United States currently has some 38,000 thousand troops in Afghanistan -- about 30,000 serving as part of NATO's 60,000-strong contingent.