NATO warned on Tuesday that its warplanes will bomb former civilian facilities if Moammar Gadhafi's forces use them to launch attacks, as the UN said Libya's capital is suffering shortages of fuel, medicine and cash.
The alliance warned it would target facilities including factories, warehouses and agricultural sites being used by loyalist troops.
The warning came a day after foreign reporters were taken to Zliten, east of Tripoli, by government minders and shown what they were told was the remains of a clinic hit by a NATO bomb that killed seven people.
Alliance military spokesman Col. Roland Lavoie said in Brussels that in recent days NATO had hit a concrete factory near Brega where regime forces were hiding and firing multibarrel rocket launchers.
"Pro-Gadhafi forces are increasingly occupying facilities which once held a civilian purpose," Lavoie told reporters in a video conference from the operation's headquarters in Naples, Italy.
"By occupying and using these facilities the regime has transformed them into military installations from which it commands and conducts attacks, causing them to lose their formerly protected status and rendering them valid and necessary military objectives for NATO," Lavoie said.
Earlier, NATO said it had "no evidence" that civilian facilities were hit in air raids near Zliten on Monday.
NATO's daily operational update said it had also hit a military facility, armoured vehicles, tanks and light military vehicles around Brega on Monday.
It also hit a command centre, antiaircraft weapons, multiple rocket launchers and a military vehicle in the Tripoli area and armoured fighting vehicles near Garyan.
The United States' top military officer, Adm. Michael Mullen, spoke on Monday of "stalemate" in NATO's Libya campaign, but still voiced optimism that Gadhafi would go.
"We are, generally, in a stalemate," the chairman of the U.S. Joint Chiefs of Staff said in Washington, but added that NATO attacks had "dramatically attrited (reduced) his forces."
"In the long run, I think it's a strategy that will work . (toward) removal of Gadhafi from power," Mullen said.
Baghdadi Mahmudi, the Libyan premier, reiterated on Tuesday that Gadhafi's departure is "not up for discussion," after meeting UN special envoy to Libya Abdul Ilah al-Khatib.
"The departure from power of Col. Gadhafi is not up for discussion," he told a news conference after British Foreign Secretary William Hague demanded on Monday that Gadhafi step down but said he might be allowed to stay in the country.
"With all due respect to the British foreign minister, it is not up to him to take decisions on behalf of the Libyan people."
Speaking before meeting French counterpart Alain Juppe, Hague said Britain would prefer for Gadhafi to leave Libya and stressed that London and Paris were "absolutely united" in NATO's current mission against Gadhafi.
"What is absolutely clear, as Alain (Juppe) has said, is that whatever happens, Gadhafi must leave power."
UN Humanitarian Co-ordinator for Libya Laurence Hart said Monday the weeklong fact-finding UN mission to Libya had identified several problems besetting Gadhafi's regime, particularly in the health sector.