Colin Powell CBS News Former Secretary of State Colin Powell spoke cautiously Sunday about any possible Syrian intervention, warning that the two-year-old civil war was likely beyond U.S. capabilities to affect any meaningful change.

"I have no affection for Assad," Powell told Bob Schieffer on CBS' "Face the Nation," while mentioning he knows the Syrian president and has personally dealt with him. "He's a pathological liar."

However, Powell said, "I am less sure of the resistance. What do they represent? Is it becoming even more radicalized with more al Qaeda coming in, and what would it look like if they prevailed and Assad went? I don't know."

Calls for U.S.-led intervention have intensified in recent days after horrifying video footage emerged of an alleged chemical attack on Aug. 21. A senior administration official harbored "very little doubt" the Assad regime was behind the attack, despite their denials.

"In both Egypt and Syria, America has to take a much more clever role," Powell said. "We shouldn't go around thinking that we can really make things happen. We can influence things and we can be ready to help people when problems have been resolved or one side has prevailed over the other."

"To think that we can change things immediately just because we're America, that's not necessarily the case," Powell said. "These are internal struggles."

His comments are in stark contrast to Sens. John McCain and Lindsey Graham, who both have called for "limited military actions ... that can change the balance of power."

In a joint statement from both Republicans, they said "the longer the conflict in Syria goes on, the worse and worse it gets and the more it spreads throughout the region."

A retired four-star general, Powell served as Secretary of State during the Bush administration from 2001-2005. His testimony to the United Nations in 2003 was instrumental in garnering international support for the Iraq war.

Many Americans oppose Syrian intervention even if there is confirmation that chemical weapons were used.

You can watch his full interview below: