"This is not a question of whether we or our allies can do this. We can do it," Gates told reporters aboard his plane after a visit to Bahrain.
"The question is whether it's a wise thing to do and that's the discussion that's going on at a political level," he said.
Gates, who has emerged as a skeptic on taking military action in Libya within President Barack Obama's administration, said last week that a no-fly zone would be a major operation and suggested it could provoke an anti-Western backlash in the region.
But he said Saturday that he wanted to make clear that the US military and allied countries had the capacity to shut down the Libyan regime's air force if ordered.
"If we are directed to impose a no-fly zone, we have the resources to do it. I just want to make clear we have the capacity to do it."
At a meeting of NATO defence ministers on Thursday in Brussels, the alliance delayed any decision on launching a no-fly zone against Libya and called for more military planning.