The morning after President Obama's speech to the nation on Libya, Senators had the chance to hear from the military commander of NATO, as both parties pressed for answers on U.S. involvement in Libya.

U.S. Navy Admiral James Stavridis said he was "comfortable" with the mission as it had been laid out so far, though he sidestepped repeated questions about what would happen.

"When you look historically at different leaders, sometimes they stay and they fight and they die, and sometimes they crack, give up and leave the country," Stavridis told Senators.

"You can see a wide range of possibilities out ahead of us," the Admiral said to Sen. John McCain (R-AZ), who both praised and jabbed at the Obama Administration, arguing that the U.S. should have done something three weeks earlier.

"The fact that there's not yet an exit strategy is not troubling to you?" asked Senate Armed Services Chairman Sen. Carl Levin (D-MI).

"It's very early in the process," the Admiral responded.

Stavridis ran down for Senators the makeup of the chain of command for this NATO mission, which will have an Italian three-star Admiral in charge of maritime forces, a three-star Canadian General in charge of the joint task force, while the air assets are under the command of American and French three-star Generals from a NATO air base in Turkey.

Still there was a sense of unease among Senators.

"Who's next?" asked Sen. Scott Brown (R-MA). "Under what circumstances do we do the same thing with other countries?"

"Are we going to be the Northern light for the entire region?" Brown added.

"How do we define success in Libya?" asked Sen. Kelly Ayotte (R-NH).

As for Adm. Stavridis, he never wavered in his calm, military assessment of the situation.

"It is clear to me what the North Atlantic Council has tasked me with," the Admiral told Sen. Levin.

"I am comfortable with that mission."

As for the makeup of rebel groups, the Admiral told Sen. Jim Inhofe (R-OK) that there were "flickers" of intelligence indicating that terror groups like Al Qaeda and Hamas were trying to get involved with the anti-Qaddafi forces, but no concrete evidence.

"We'll continue to look at that very closely as part of doing due diligence as we move forward on any kind of relationship" with the rebels, the Admiral said.

But the bottom line for many was simple.

"Do you have an estimation of the timetable, how long you think we'll be there?" asked Sen. Joe Manchin (D-WV).

"I think it's very difficult to ascertain that," the Admiral responded.