Washington, April 12 (IANS) Libyan leader Muammar Gaddafi's departure from power is "non-negotiable", Xinhua Tuesday quoted a US State Department spokesman as saying.

"We've said it's our bottom line, it's a non-negotiable demand," US State Department spokesman Mark Toner told reporters, adding that "we believe he needs to depart power, he needs to step down, he's delegitimised as a leader".

He, however, acknowledged that there is "a difficult situation" in Libya as the north African state is currently split in half.

An African Union (AU) delegation, headed by South African President Jacob Zuma, is mediating a political solution in Libya, and Gaddafi has agreed to its four-point peace plan which calls for ending fighting, facilitating humanitarian assistance, protecting foreign nationals and discussing political transition and reform.

US Secretary of State Hillary Clinton reiterated Monday that the US wants to see a ceasefire, and the Libyan government forces "pull back from the areas that they have forcibly entered" and a resumption of water, electricity and other services to cities that "have been brutalised by the Gaddafi forces".