The Arizona Republican, who was defeated by President Obama in the 2008 presidential election, spoke in a wide-ranging interview that aired Sunday on CNN's "State of the Union."
"I think the great danger now is a half-measure, sort of a -- you know, try to please all ends of the political spectrum," McCain told CNN chief national correspondent John King. "And, again, I have great sympathy for the president, making the toughest decisions that presidents have to make, but I think he needs to use deliberate speed."
Disregarding requirements that have been "laid out and agreed to" by Central Command head Gen. David Petraeus and Joint Chiefs of Staff Chairman Adm. Michael Mullen "would be an error of historic proportions," McCain said when asked whether 10,000 or 20,000 additional troops in Afghanistan would suffice.
Also Sunday, Sen. Dianne Feinstein, head of the Senate Intelligence Committee, said U.S. troops would be put in "jeopardy" if Obama does not listen to McChrystal.