The month of July is on track to be the deadliest month for U.S.-led international forces in Afghanistan since the war began eight years ago.
At least 46 international troops and 24 Americans have been killed in Afghanistan during this month.
U.S. and British forces have been pushing into the southern region of the country with a massive offensive against the Talibam. The operation is in its second week. Casualties have been running high, at an average of about three a day.
In Washington, Pentagon spokesman Geoff Morrell acknowledged the "alarming rate" at which U.S. military personnel were being killed.
He told reporters that July has been "an extraordinarily difficult month for all of us who are so heavily invested in trying to better the situation in Afghanistan."
At least 107 U.S. coalition troops have been killed this year, which is higher than 2008's total of 155 U.S troop deaths in Afghanistan, according to icasualties.org. U.S. officials expected higher casualty rates ever since President Obama ordered 21,000 additional U.S. troops to Afghanistan this year.
There are about 57,000 U.S. troops currently serving in Afghanistan, and that number is expected to rise to at least 68,000 by the end of this year.
On Tuesday, Obama said that he hopes military operations in Afghanistan can move to a different phase after the Afghan presidential election on Aug. 20.