Libyan interim government fighters have launched what they say is the “final assault” on the loyalist stronghold of Sirte, as officials pledged to appoint a new transitional government soon after the strategic coastal city is captured.

National Transitional Council forces seized new territory in and around Sirte on Monday. The gains included the nearby small town of Qasr Abu Hadi, where former leader Moammar Gadhafi was reportedly born in a nomad tent in 1942.

The clashes Monday killed four anti-Gadhafi fighters and wounded 39 others.

A Red Cross convoy delivered oxygen and other urgently needed medical supplies to the Ibn Sina hospital in Sirte after an earlier attempt was aborted due to heavy fighting. Fleeing medics said patients were dying on the operating table at the facility because there was no oxygen and no fuel for the hospital's generators.

In Tripoli, Libya's transitional leaders vowed to step down after Sirte is secured and the country's liberation declared. Interim Prime Minister Mahmoud Jibril said he has requested that the declaration be announced after Sirte is captured because that would ensure all of Libya's sea, land and air entry ports are secure.

He acknowledged that fighting will continue in a number of pockets deep in the southern desert, including Bani Walid. But he said it is important to declare victory and begin rebuilding the country.

Jibril and NTC head Mustafa Abdel Jalil already had pledged to take no further part in the country's future government, as required by the country's interim constitution. The pledge was intended to reassure the public they will not suffer under another dictatorship.

Meanwhile, NATO said Monday it is concerned about a German magazine report that says the alliance has lost track of 10,000 surface-to-air missiles in Libya. Der Spiegel said Sunday that NATO's top military officer, Admiral Giampaolo Di Paola, told German lawmakers about the missiles during a confidential briefing last week.

A spokesman for the admiral said he could not confirm the report.

NATO Secretary-General Anders Fogh Rasmussen said Monday that stockpiles of weapons that are not properly controlled and monitored are a matter of concern, and that the NTC is responsible for overseeing weapons in Libya.