Libya could become a peaceful democracy or face years of civil war, US Secretary of State Hillary Clinton has told Congressional lawmakers.
Mrs Clinton appeared on Capitol Hill to urge Congress not to cut funds needed to deal with crises abroad.
Meanwhile, US Defence Secretary Robert Gates said the US was weighing "a lot of options and contingencies".
The comments came a day after the US began repositioning warships and military aircraft in the Libya region.
In Washington on Tuesday, senior officials in President Barack Obama's administration maintained pressure on Libyan leader Col Muammar Gaddafi to step down from power.
At the Pentagon, Mr Gates said the US military aimed to give Mr Obama "the broadest possible decision space", while emphasising that no decision on a course of action had been made.
He said 400 US Marines had been deployed to assist in humanitarian and evacuation efforts.
Meanwhile, Mrs Clinton reiterated demands that Col Muammar Gaddafi "must go now, without further violence or delay".
"The entire [Middle East] region is changing, and a strong and strategic American response will be essential," Mrs Clinton said to the House of Representatives Foreign Affairs Committee in prepared testimony.
"In the years ahead, Libya could become a peaceful democracy, or it could face protracted civil war. The stakes are high.
"And this is an unfolding example of how we use the combined assets of diplomacy, development and defence to protect our interests and advance our values."
She added that the US was working to translate the "world's outrage into action and results".
The US ambassador to the UN, Susan Rice, told reporters in Washington that the US would continue to place pressure on Col Gaddafi until he resigns, while working to stabilise oil prices and avert a possible humanitarian crisis.
"We are going to keep the pressure on Gaddafi until he steps down and allows the people of Libya to express themselves freely and determine their own future," Ms Rice told US media.
Mrs Clinton has said the US is still considering the implementation of a no-fly zone in Libya, although she acknowledged there would be drawbacks in such a move.
Defence officials have said the US would have to destroy Libyan air defences in order to establish and enforce a no-fly zone in the country.
"If we were to set it up... we'd have to work our way through doing it in a safe manner and not put ourselves in jeopardy," chairman of the Joint Chiefs of Staff Adm Mike Mullen told reporters, referring to the threat posed by Libyan air defence measures.
Separately on Tuesday, Gen James Mattis, a top US military commander in the Middle East, added that a no-fly zone would deter Col Gaddafi's regime from bombing demonstrators as they protested against the government.
If such measures were taken, US commanders could turn to the USS Enterprise, currently in the Red Sea, as well as the amphibious ship the USS Kearsarge, which has a fleet of helicopters and about 2,000 Marines aboard.
Meanwhile, Col Gaddafi has played down protests in the country and insisted that all his people love him. His comments came amid reports that he is attempting to regain control of rebel areas in western Libya.