Nato Secretary General Anders Fogh Rasmussen has told a foreign ministers' summit the alliance needs "a few more" aircraft for its mission in Libya.
Mr Rasmussen said he had received no offers from any ally at the meeting in Berlin to supply the extra warplanes, but he remained hopeful.
Nato would continue "day by day, strike by strike" to target Col Muammar Gaddafi's forces, he told media.
Britain and France have been trying to persuade other Nato members to do more.
London and Paris have been urging allies to get actively involved with ground attack planes to intensify air raids, says BBC diplomatic correspondent James Robbins, who was at the Berlin news conference.
But he says that while UK Foreign Secretary William Hague insisted Nato was more united than ever, the meeting has so far left unanswered the question of which other countries are willing to join the active combat role.
There are divisions in the alliance, with Turkey and Germany opposed to the Libya mission.
Mr Rasmussen told the meeting that Nato supreme commander, the US Admiral James Stavridis, was "generally content" with his forces.
But the secretary general added: "Now they [pro-Gaddafi forces] hide their heavy arms in populated areas where before many targets were easy to get to.
"To avoid civilian casualties we need very sophisticated equipment so we need a few more precision fighter ground-attack aircraft for air-to-ground missions."
He added: "I am confident that nations will step up to the plate," although when pressed, he said: "I don't have specific pledges or promises from this meeting".
As Mr Rasmussen spoke, Nato warplanes bombed targets around the Libyan capital, Tripoli. There were loud explosions, followed by heavy anti-aircraft fire.
The BBC's Jeremy Bowen was one of a group of journalists taken to a university cafeteria in the city afterwards by government officials.
He says the glass was smashed and doors appeared to have been blown off by a blast.
Students there said 8-10 people had been injured by flying glass. They said the raid had targeted a military installation 500m away.
Libyan state TV said three people were killed in a strike, but a Nato official dismissed the report.
"Nato has seen these reports and the allegations of civilian casualties in Tripoli... We have seen these allegations before and they have proved to be misinformation, which is the case today," the Nato official told Reuters.
Libyan TV later broadcast pictures which appeared to show Col Gaddafi surrounded by cheering supporters as he stood through the sunroof of a car driving through Tripoli, pumping his fists in the air.
Fighting has continued in the rebel-held city of Misrata, western Libya, which has been besieged by pro-Gaddafi forces for nearly two months.
A rebel spokesperson, Ghassan, told Reuters the port area had been heavily shelled by government forces, forcing its closure.
Rebels also said a rocket attack by pro-Gaddafi forces killed 23 people on Thursday morning, but this again cannot be independently verified.
Koussa sanctions lifted
Some assessments suggest that Nato only needs about a dozen or so extra strike aircraft to maintain the tempo of operations.
Only a few of Nato's 28 members - including France, the UK, Canada, Belgium, Norway and Denmark - are conducting air strikes.
Washington withdrew its fighter jets as it scaled back its role in the mission, although US planes are still targeting Col Gaddafi's air defences and it says it has still been flying a third of the missions.
Asked on Thursday if American forces could resume ground strikes, Mr Hague said the US was already making "a huge contribution".
"It's not unreasonable to ask other nations... to make additional contributions," Mr Hague added.
Several major Nato member countries, including Spain and Italy, have not taken part in attacks on ground targets.
Spain said on Thursday it would continue to provide aircraft without joining directly in such raids.
Italy is also refraining from carrying out air strikes, but it allows missions to be flown from its territory.
Meanwhile, Moussa Koussa, the Libyan foreign minister who fled to the UK late last month, is no longer subject to EU sanctions, the British government said.
Earlier, the "Brics" group of five emerging nations - Brazil, Russia, India, China and South Africa - met in southern China and said "the use of force should be avoided" in Libya.