US Secretary of State Hillary Clinton said Libya must end violence against protesters seeking to end Colonel Muammar Gaddafi's 41-year rule and the United States would take "appropriate steps" in time.
"As we gain a greater understanding of what actually is happening - because you know, of course, that communication has been very effectively shut down and we are trying to gather as much information as possible - we will take appropriate steps in line with our policies, our values and our laws," she told reporters.
"But we are going to have to work in concert with the international community."
The US government faced mounting calls for action against Libya earlier today as Muammar Gadafy's security forces used tanks, helicopters and warplanes to unleash fresh attacks on pro-democracy demonstrators.
But US options to influence events in Libya appear limited, unlike in Egypt and Bahrain where Washington was able to bring pressure to bear on long-time allies to soften their response to popular uprisings.
"The US has relatively little leverage in Libya. There are certainly US interests but they are more global interests
- and that is mostly oil," said Daniel Byman of the Brookings Institution think tank in Washington.
"Libya was an adversary of the United States for most of Gadafy's rule and, while there has been a rapprochement, they have never been terribly close."
US foreign aid to Libya was less than $1 million in 2010, a congressional aide said, although trade has flourished since Washington began to lift sanctions in 2004. Last year, US exports to Libya were $665 million, while imports were $2.12 billion.
Ali Aujali, who has resigned as Libya's envoy to the United States, urged Washington to raise its "voice very strongly."
"Please, please, help the Libyan people. Help them. They are burning," Aujali said on ABC's Good Morning America.
White House spokesman Jay Carney urged Libya's government to respect the rights of its citizens and said Washington would work with the international community to speak "with one voice in condemning the violence."
Libyan security forces have cracked down fiercely on demonstrators across the country, with fighting spreading to the capital Tripoli after erupting in Libya's oil-producing east last week, in a reaction to decades of repression.
Carney said US Secretary of State Hillary Clinton would speak about the situation in Libya later in the day.
US Senator John Kerry, the influential chairman of the Senate Foreign Relations Committee who is close to Obama, called on the administration to consider imposing new sanctions on Libya and on energy companies to take action as well.
"All American and international oil companies should immediately cease operations in Libya until violence against civilians ceases," he said in a statement.
Agencies