The President's remarks tonight come during what seems to be a momentum shift in Libya -- the rebels, aided by the U.S. and European-engineered no-fly zone and bombing of Gadhafi's strongholds, have advanced on Gadhafi's hometown and reclaimed two critical oil-producing areas.
But no one expects Gadhafi to be ousted from power easily. The American general who has overseen much of the bombing against Gadhafi's forces urged the rebels to slow down or they might be "destroyed."
"Among my concerns right now is that the opposition will overreach in their haste to move west. They are not a match for the regime forces. If they move hastily and get destroyed, then there's nothing to stop regime from moving right back down the coast road," Gen. Carter Ham told ABC's Martha Raddatz.
Recent polls show that Americans generally support the military operations in Libya, but they're looking to the president to address the many unanswered questions about what's next.
There is support for the action on both sides of the political aisle, but Republicans in particular have said the President did not do a good enough job justifying the action before committing American forces.
NATO is set to take over command of the operation, but the Americans Navy and Air Force are still very much involved enforcing a no-fly zone over Libya.
The full transfer of command to NATO will be complete in several days. But Defense Secretary Robert Gates would not give a firm deadline for just how long U.S. involvement would last.
"Will the mission be over by the end of the year?" he was asked by ABC's Jake Tapper on Sunday.
"I don't think anybody knows the answer to that," Gates said.
Establishing the no-fly zone is described as a humanitarian effort, authorized by the United Nations Security Council, to keep Gadhafi from slaughtering rebels who hope to push him out of power.
"Imagine we were sitting here and tens of thousands of people had been slaughtered. The cries would be, 'Why did the United States not do anything?'" said Secretary of State Hillary Clinton on ABC's "This Week" Sunday.
But the aim of the U.S. is not just to keep Gadhafi's give the rebels a fighting chance. At the same time, President Obama said Gadhafi must leave power. The distinction between avoiding a slaughter of civilians and working to oust him has created a great deal of confusion about what the U.S. and its European allies are trying to accomplish.
There is much concern on Capitol Hill that it will be difficult or impossible for the United States and NATO to disengage from Libya now that military force has been used.
Americans are particularly leery after nearly a decade of military engagement in Iraq and Afghanistan. Budget watchers say the first week of bombing and air support in Libya cost more than $600 million.
"If the American people are uncertain as to our military objectives in Libya, it is with good cause," said Sen. Mitch McConnell, the top Republican in the Senate on Monday. "The president has failed to explain up to this point what follows the evident establishment of a no-fly zone over Libya as it was originally described. Further, the president has articulated a wider political objective of regime change in Libya. That is not the stated objective of our military intervention, nor is it the mandate of the UN resolution that the president has used as a justification for our military efforts there."