"As long as Gaddafi remains in power, unless he changes his approach and provides the Libyan people an opportunity to express themselves freely and there are significant reforms in the Libyan government, unless he is willing to step down, that there are still going to be potential threats towards the Libyan people," Obama said.
The US President was responding to a question about the duration of the Libyan mission at a joint press availability with his counterpart Mauricio Funes of El Salvador in San Salvador.
"I think fairly shortly we are going to be able to say that we've achieved the objective of a no-fly zone. We will also be able to say that we have averted immediate tragedy," he said.
Obama said US will continue to support the efforts to protect the Libyan people, but will not be in the lead.
"That's what the transition that I discussed has always been designed to do. We have unique capabilities. We came in, up front, fairly readily, fairly substantially, and at considerable risk to our military personnel.
And when this transition takes place, it is not going to be our planes that are maintaining the no-fly zone.
It is not going to be our ships that are necessarily involved in enforcing the arms embargo. That's precisely what the other coalition partners are going to do," he said.
This is the reason why building this international coalition has been so important because it means that the US is not bearing all the cost.
"It means that we have confidence that we are not going in alone, and it is our military that is being volunteered by others to carry out missions that are important not only to us, but are important internationally. We will accomplish that in a relatively short period of time," he said.
Obama argued that it is in America's national interest to act against authoritarians like Gaddafi who train their guns against their own people.
"We've already seen what happened in Egypt and Tunisia -- peaceful transitions. We have a huge national interest in making sure that those are successful because if Egypt can make a transition from an autocratic regime to a democracy, if Tunisia can make those same changes, they become models for a peaceful transition that at some point may be adopted by other countries in the region," he argued.
"Not only do we have a humanitarian interest, but we also have a very practical interest in making sure that the changes that are sweeping through that region are occurring in a peaceful nonviolent fashion," Obama said.
"When we can have some impact on that with a relatively modest contribution as part of a broader international effort, then I absolutely believe that the costs are outweighed by the benefits, and that is what drove my decision.
And that's why I think that we need to make sure that we see this through effectively," Obama argued.