WASHINGTON - The United States should be cautious about directly going after Libyan leader Muammar Gaddafi and his inner circle, said US Republican Senator John McCain on Sunday.

McCain made the remarks on CNN when he was asked about the idea of directly bombing Gaddafi and his inner circle, which was proposed by another Republican Senator Lindsey Graham.

"You know, we have tried those things in the past ... and it's a little harder than you think it is," said McCain, who just visited Benghazi, a stronghold of the Libyan opposition forces.

"We don't know exactly where he is. We do have to worry about civilian casualties," he said. "That could turn the Libyan people against us."

McCain, a ranking member of the US senate military committee, said the focus should be that the Libyan opposition forces win the battle on the ground, urging the United States to bring more "air assets" to the ongoing military operations on Libya.