The US on Saturday warned Libyan leader Muammar Gaddafi of "swift and sure consequences including military action" if he violated a UN Security Council resolution ordering an immediate halt to fighting.
"Gaddafi is violating the ceasefire imposed by the UN Security Council resolution," US envoy to UN Susan Rice said.
"We don't believe the military action has stopped," she told PBS.
In a separate interview with CNN, Rice warned Gaddafi of "swift and sure consequences including military action."
Five countries abstained from the resolution, which was adopted on Thursday, authorizing a no-fly zone and "all necessary measures" for protecting civilians in Libya.
China and Russia, which have veto power, abstained from voting. India, Germany and Brazil -- among the non-permanent members, also abstained.
Shortly after the resolution passed, Gaddafi declared a ceasefire.
US President Barack Obama yesterday said that Gaddafi had a "choice" to either respect the ceasefire by ending all attacks against civilians or face use of force by US, UK, France and Arab countries.
Obama also asked Gaddafi to stop his advancing troops and restore electricity, water and gas supply in rebel held towns.
"These terms are not subject to negotiations," he said.
"If Gaddafi does not comply with the resolution, the international community will impose consequences and the resolution will be enforced through military action," he said.
Obama and French President Nicholas Sarkozy have also called on Gaddafi to pull his troops out of three towns, Misrata, Zawiya, and Ajdabiya, which are under siege.
Speaking to PBS, Rice said that 700,000 civilians in Benghazi were at "extraordinary risk" but she did not clarify whether rebels, who had taken up arms against Gaddafi's regime, were considered civilians.
The US envoy did not specify the military actions that would be taken to implement the resolution.
"We have many options at our disposal," she said.
Rice said that the resolution did not authorize the attacks against Gaddafi and his supporters but it did call for legal accountability for "atrocities" committed during the crackdown on civilians and rebels.