The video conference came ahead of Mr. Obama's planned speech Tuesday night at the U.S. Military Academy West Point, N.Y., where he will outline a new U.S. war plan and dispatch between 30,000 and 35,000 more American troops to Afghanistan. Karzai's office says the two leaders discussed in detail the security, political, military and economic aspects of the strategy.
The call was one of several Mr. Obama was making to world leaders, including Asif Ali Zardari, the president of neighboring Pakistan.
Mr. Obama's war escalation includes sending more American forces into Afghanistan in a graduated deployment over the next year. They will join the 71,000 U.S. troops already on the ground. Mr. Obama's new war strategy also includes renewed focus on training Afghan forces to take over the fight and allow the Americans to leave.
Thirty thousand more troops would be 10,000 fewer than Gen. Stanley McChrystal, the commander in Afghanistan, requested, reports CBS News correspondent David Martin. The president hopes to make up at least some of the difference with contributions from NATO allies.
"I think NATO will come through with a couple thousand and so I think we'll still be somewhat short of what Gen. McChrystal proposed," Michael O'Hanlon of the Brookings Institution told CBS News.
Mr. Obama also is expected to explain why he believes the U.S. must continue to fight more than eight years after the war was started following the Sept. 11 attacks by al Qaeda terrorists based in Afghanistan.
He will emphasize that Afghan security forces need more time, more schooling and more U.S. combat backup to be up to the job on their own, and he will make tougher demands on the governments of Pakistan as well as Afghanistan.