The general said he sends Obama regular updates through the military chain of command, but has little personal contact with his commander-in-chief.
"We don't have personal conversations. We haven't recently, but we just been through the Christmas holidays, so I feel pretty comfortable the way we are," he said.
The general said he is convinced that the Afghan fight can be won, and only one thing could shake that conviction.
"I think that it would be a belief that the Afghan people have lost faith, that the future can be better and that we can help them get there. If they were to reach that point, then I think that I would sense that this would not be possible. I don't feel that now."
Despite signs of progress, the fight for Afghanistan appeared to be becoming more deadly as U.S. and NATO troops heightened their presence and increased their patrols.
Three American and three NATO soldiers died today in ambushes and roadside bombs. The latest casualties brought to 10 the number of Americans who have died so far this month, making it a bloody start to a new year of combat.
Another alarming trend is that civilian fatalities in Afghanistan rose significantly in 2009 for the second straight year, according to United Nations numbers obtained by ABC News, mostly because of growing Taliban violence rather than U.S. and coalition mistakes.
The U.N. said 2,412 civilians died in 2009, an increase of 14 percent over the prior year and nearly 60 percent over 2007.
That massive spike over the past two years reflects the mounting violence in Afghanistan that has left large pockets of the southern and eastern parts of the country virtually controlled by insurgents.
But the numbers are a success for McChrystal, who has made reducing the number of civilians killed by U.S. forces one of his top priorities.
In 2007, 41 percent of civilian fatalities were caused by the coalition. In 2008, that dropped slightly, to 39 percent. And in 2009, that percentage dropped significantly, down to 25 percent, according to the United Nations numbers.
The general's optimism comes as a new poll shows that Afghan are also believing that improvements are on the way.
The survey by ABC News, the BBC and ARD German TV found that 70 percent, a 30-point advance in views, that the country is headed in the right direction. That is the highest level of optimism since 2005.
Afghans' expectations that their own lives will be better a year from now have jumped by 20 points, to 71 percent, a new high. And there's been a 14-point rise in expectations that the next generation will have a better life, to 61 percent.
ABC News' Nick Schifrin contributed to this report