Libyan rebels slammed NATO on Tuesday, saying they were too slow to act on Libyan leader Muammar al-Qaddafi and that they were allowing Qaddafi forces to kill people in Misrata, according to Reuters.

"Either NATO does it work properly or we will ask the Security Council to suspend its work," said Abdel Fattah Younes, head of the rebel forces, told Reuters.

"NATO is moving very slowly, allowing Qaddafi forces to advance," he added. "NATO has become our problem."

This comes as NATO said Tuesday that Qaddafi forces loyal are using human shields.

The alliance said Qaddafi's forces had changed tactics in the besieged western city of Misrata by moving tanks and other heavy equipment to civilian areas to prevent pilots from targeting them. 

Brig. Gen. Mark Van Uhm of NATO said its U.N.-authorized aerial onslaught to stop Qaddafi from attacking dissenters has so far destroyed 30 percent of the Qaddafi's weapons. On Monday alone, the alliance said it carried out 14 attacks on ground targets across the country, destroying radars, munitions dumps, armored vehicles and a rocket launcher.

Three-quarters of Monday's scheduled strike missions, however, had to return without dropping their bombs or launching their missiles because of Qaddafi loyalists made it more difficult for pilots to distinguish between civilians and regime troops, Van Uhm said.

A doctor in Misrata corroborated that, saying Qaddafi's forces have been placing heavy weapons near civilians there for the past two weeks.

"They snuck their anti-aircraft weapons and tanks into the city. They are between the apartment buildings and the trees," said the doctor, who spoke on condition of anonymity for fear of reprisals. "They disguise their equipment on the big agricultural trucks that the farmers use outside of town. They bring in mortars with civilian cars."

The opposition has controlled much of the eastern half of Libya since early on in the uprising that began in February. Misrata is one of two major cities in the west that have also risen up against Qaddafi's regime, which has responded with a brutal crackdown waged over weeks of battles.

The other front is on a coastal road leading out of the rebel stronghold city of Benghazi in the east toward the capital Tripoli in the west. Qaddafi loyalists and opponents have fought a tug-of-war for weeks on the road, with a few main towns and oil ports changing hands repeatedly. Though Qaddafi's forces are stronger, NATO airstrikes have helped the rebels hold back an onslaught on the east.

The regime has softened its public stance against any compromise that would end the fighting and is putting out feelers for a ceasefire, though it continues to resist rebels' demand that Qaddafi step down. Qaddafi's British-educated son Seif al-Islam Qaddafi, on Tuesday, dismissed reports that his father's inner circle of advisers was crumbling following the defection of Foreign Minister Moussa Koussa.

On the coastal road leading from the east to Tripoli, the rebels had managed to take part of the oil town of Brega on Monday, aided by an international air campaign. But the rocket and artillery salvos unleashed on the rebels Tuesday indicated the government's offensive capabilities remain very much intact.

"When you see this, the situation is very bad. We cannot match their weapons," said Kamal Mughrabi, 64, a retired soldier who joined the rebel army. "If the planes don't come back and hit them, we'll have to keep pulling back."

Rebel attempts to fire rockets and mortars against the government forces were met with aggressive counter bombardments that sent many of the rebel forces scrambling back all the way to the town of Ajdabiya, dozens of miles (kilometers) away. There did not appear to be any immediate response from the international aircraft patrolling the skies that have aided the rebels in the past.

Earlier in the day, however, there was an airstrike against a convoy of eight government vehicles advancing toward rebel positions, rebel officer Abdel-Basset Abibi said, citing surveillance teams.

Rebel forces have been helped by the arrival on the front of more trained soldiers and heavier weapons, but they are still struggling to match the more experienced and better equipped government troops, even with the aid of airstrikes.

Late Monday, Government spokesman Moussa Ibrahim reiterated Qaddafi's refusal to step down, as the opposition is demanding. He said any changes in Libya must be led by Qaddafi, who has ruled the country for more than four decades.

"We could have any political system, any changes: constitution, election, anything, but the leader has to lead this forward," he said in Tripoli.

"Don't decide our future from abroad. Give us a proposal for change from within," Ibrahim said, chastising Western powers who have a "personal problem with the leader" and economic interests they believe would be better served if Qaddafi's government collapsed.

The comments were unlikely to appease the rebels fighting to oust the Libyan leader who has a legacy of brutality. Any long-term settlement poses tough questions about the fate of Qaddafi's family and the new leader of a post-Qaddafi nation, and the opposition has rejected any solution that would involve one of his sons taking power.

President Barack Obama's envoy to the opposition, Chris Stevens, was meeting with members of Libya's Transitional National Council in Benghazi to get a better idea of who they are, what they want and what their needs and capabilities are, a U.S. official said. His visit could pave the way for U.S. recognition of the council as Libya's legitimate government although no decision is imminent, the official said.

Stevens was the No. 2 at the U.S. embassy in Tripoli until the mission was shuttered in February amid escalating violence. He will be discussing humanitarian and possible financial assistance to the opposition, the official said. The official spoke on condition of anonymity pending an announcement of the visit by the White House on Tuesday.

Three countries, including NATO allies France and Italy, along with Qatar, have recognized the transitional council as the legitimate representatives of the Libyan people but the United States has yet to follow suit. The U.S. has also not made a decision on whether to arm the rebels.

The Associated Press contributed to this report.