By Maria Golovnina and Michael Georgy
TRIPOLI (Reuters) - The United States accused Libyan leader Muammar Gaddafi on Friday of defying international demands for an immediate ceasefire, hours after President Barack Obama said he faced military action if he did not comply.
A U.S. National Security official said Gaddafi's forces were continuing to advance toward the eastern rebel stronghold of Benghazi, despite a ceasefire announcement by the Libyan government earlier in the day.
In Benghazi, rebels said they feared an attack by Gaddafi's forces, while in the western rebel-held city Misrata, residents said they had faced a day of heavy bombing.
"All attacks against civilians must stop," Obama said, a day after the U.N. Security Council passed a resolution authorizing international military intervention to protect civilians in Libya.
Underlining a commitment to provide protection to people across the country -- and not just in the rebel-held east -- Obama also specifically called on Gaddafi's forces to pull back from the western cities of Zawiyah and Misrata, as well as the eastern town of Ajdabiya:
"Gaddafi must stop his troops from advancing on Benghazi, pull them back from Ajdabiya, Misrata and Zawiyah, and establish water, electricity and gas supplies to all areas. Humanitarian assistance must be allowed to reach the people of Libya ...
"Let me be clear, these terms are not negotiable ... If Gaddafi does not comply ... the resolution will be enforced through military action."
His comments were echoed in a statement that Paris issued on behalf of the United States, Britain, France and Arab states.
GADDAFI TROOPS ADVANCING, OFFICIAL SAYS
In Washington, a national security official, who spoke on condition of anonymity, said the troop movements by Gaddafi's forces toward Benghazi were "purposeful".
The assessment was based on official reporting reaching U.S. national security agencies in Washington, he said.
Asked by CNN whether Gaddafi was in violation of the U.N. resolution, the U.S. envoy to the United Nations, Susan Rice, said: "Yes, he is."
In Tripoli the government said there had been no bombing since it announced the ceasefire.
"We have had no bombardment of any kind since the ceasefire was declared," Deputy Foreign Minister Khaled Kaim told journalists when asked about reports of continued government operations in Misrata and other parts of the country.
Kaim said Libya was asking China, Germany, Malta and Turkey to send observers to monitor its adherence to the ceasefire.
A doctor in Misrata contacted by phone in the evening said there had been heavy bombing through the day.
"Now they are on the outskirts of the city and I can still hear bombing from time to time," he said.
Rebels in Benghazi dismissed Gaddafi's ceasefire declaration as a ruse.
"He is lying. His troops are advancing. We don't believe what Gaddafi says," said Mohammed Ishmael al-Tajouri, from the rebel coalition in Benghazi. "When he comes to Benghazi he will be fighting. There is no negotiating with Gaddafi."
French Foreign Minister Alain Juppe said everything was ready to launch military strikes in Libya. France and Britain have both been strong advocates of military action.
After embarking on wars in Afghanistan and Iraq, the United States had insisted it would participate in rather than lead any military action. Obama said the United States would not deploy ground troops in Libya.
(Additional reporting by a Reuters reporter in Benghazi, Mariam Karouny and Tarek Amara in Tunisia, Louis Charbonneau and Patrick Worsnip at the United Nations and John Irish in Paris; writing by Myra MacDonald; Editing by Kevin Liffey)