NATO must broaden the range of targets it is bombing in Libya or risk failing to remove Moammar Gadhafi from power, Britain's most senior military officer was quoted as saying on Sunday.
NATO warplanes, acting under a United Nations mandate to protect civilians, have stopped government troops advancing on rebel strongholds but the collapse of Gaddafi's rule, which many Western governments seek, has not materialized.
After a fresh series of air strikes on his Bab al-Aziziyah compound in Tripoli, Gadhafi taunted the Western military alliance, saying in an audio recording aired on Friday that he was in a place where NATO could not reach him.
General David Richards, Britain's chief of defense staff, said the military campaign to date had been a "significant success" for NATO, but it needed to do more.
"If we do not up the ante now there is a risk that the conflict could result in Gadhafi clinging to power," he was quoted in the Sunday Telegraph newspaper as saying.
"At present, NATO is not attacking infrastructure targets in Libya. But if we want to increase the pressure on Gadhafi's regime then we need to give serious consideration to increasing the range of targets we can hit," he told the paper.
At nightfall Sunday, NATO aircraft blasted an oil terminal in the key eastern city of Ras Lanouf, Libyan TV reported.
The Libya TV report said the bombs hit methanol tanks, causing leaks. NATO officials had no immediate comment.
The rebel-held city of Misrata, scene of some of the fiercest fighting in the conflict, was calm but rebels said they were braced for renewed attacks by forces loyal to Gadhafi.
Nearly three months after a revolt began against Gadhafi's four-decade rule, fighting between rebels and government forces on several fronts has come to a near-standstill and Gadhafi is refusing to bow to efforts to force him from power.
His foreign minister, Abdelati Obeidi, sounded a defiant note when he met in Tripoli with Abdelilah al-Khatib, the United Nations special envoy to Libya.
"The Libyan people will not kneel and will not give in," the state-run Jana news agency quoted Obeidi as saying.
The uncertain direction of the Libya conflict creates a dilemma for Western governments. They face voters who are impatient for quick results and want to avoid a repeat of the long-drawn out fighting in Iraq and Afghanistan.
An inconclusive outcome is likely to limit Libyan oil exports, keeping world prices high, and also to drive thousands more migrants to make the hazardous journey across the Mediterranean to Europe in leaky boats.
Previous NATO bombing campaigns, especially in Kosovo in the late 1990s, showed that more aggressive targeting carries with it the risk of civilian casualties.
Libya on Saturday held a funeral for nine imams, or Muslim clerics, it said NATO killed in an air strike on the eastern city of Brega a day earlier. The alliance said the building it struck in Brega was a command-and-control-center.
Thousands of people have been killed in the conflict in Libya, the bloodiest of the revolts which have convulsed the Middle East in what has been described as the "Arab spring."
Libyan officials deny killing civilians, saying instead they were forced to take action against criminal armed gangs and al Qaeda militants. They say the NATO campaign is an act of colonial aggression aimed at grabbing Libya's oil.
Tunisia's state news agency reported that a boat arrived at the south-eastern port of Zarzis carrying three officers who had defected from Gadhafi's security forces.
It did not give their rank, but said they joined several other Libyan officers who had arrived in Tunisia by boat in the past few days, suggesting that there were divisions inside the ranks of Gaddafi's security forces.
However, in Tripoli -- where foreign reporters operate under restrictions on their movement -- the outward signs were that Gadhafi's administration was holding firm.
Security officials in North Africa and elsewhere say one of the risks from a lingering conflict in Libya is that al Qaeda's north African branch could exploit the chaos to acquire weapons and recruit followers.
A Tunisian security official told Reuters on Sunday that two suspected al Qaeda members had been arrested near the border with Libya carrying an explosives belt and several bombs.
In Misrata over the past few days the rebels have pushed government troops out of most parts of the city and captured the airport, but the city and its sea port -- the only supply route -- are still within range of pro-Gaddafi artillery.
"The (pro-Gadhafi) brigades still have military equipment enabling them to bombard any area in Misrata. You can expect anything from them because they behave like criminal gangs," a rebel spokesman called Abdelsalam said from the city.
Pro-Gaddafi forces have bombarded the city for weeks, killing hundreds, although the rebels have held out with help from NATO air strikes.
"There are skirmishes every now and then mainly in the eastern area of Kararim. The brigades opt for tactical retreats before launching attacks, using missiles and mortars," he said.
"The revolutionaries are in full control of the port but the danger is still there because the brigades have tanks and rocket-launchers."