BREGA, Libya (AP) -- Libyan government forces unleashed a withering bombardment of rebels outside a key oil town Tuesday as an Obama administration envoy met with the opposition leadership in its de facto capital, a possible step toward diplomatic recognition.

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NATO said nearly a third of Libyan leader Moammar Gadhafi's heavy weapons have been destroyed. But the alliance said Gadhafi'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.

A doctor in Misrata corroborated that, saying Gadhafi'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 Gadhafi'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. Gadhafi 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 Gadhafi'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 Gadhafi step down. Gadhafi's British-educated son Seif al-Islam Gadhafi, 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.

Brig. Gen. Mark Van Uhm of NATO said Tuesday its U.N.-authorized aerial onslaught to stop Gadhafi from attacking dissenters has so far destroyed 30 percent of the Gadhafi'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 Gadhafi loyalists made it more difficult for pilots to distinguish between civilians and regime troops, Van Uhm said.

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 Gadhafi's refusal to step down, as the opposition is demanding. He said any changes in Libya must be led by Gadhafi, 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 Gadhafi'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 Gadhafi's family and the new leader of a post-Gadhafi 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 head of the African Union, meanwhile, voiced his support for Gadhafi, calling for the end to foreign interference into what he called an internal Libyan problem.

Teodoro Obiang Nguema, 69-year-old president of Equatorial Guinea, described Western military efforts to enforce a no-fly zone over Libya as a "so-called humanitarian intervention."

The rebels have seen success in their efforts to establish an internationally recognized government in eastern Libya, forging tighter links with Britain and Italy, both potentially major markets for Libyan oil. Italy offered diplomatic recognition to the Libyan opposition council on Monday, becoming the third country to do so after France and Qatar.

A tanker arrived near the eastern city of Tobruk on Tuesday to load up the rebels' first shipment of oil for export, potentially giving them crucial funding.

The tanker can carry 1 million barrels of oil, less than the 1.6 million barrels Libya produced even day on average before the crisis. Analysts viewed the delivery as a symbolic step forward.

The conflict in Libya caused crude exports from the country, 17th among the world oil producers, to dwindle to a trickle, sparking a surge in global oil prices. Benchmark crude was trading at around $108 a barrel on Tuesday.

Gadhafi's son Seif al-Islam shrugged off the notion that the regime was disintegrating after the foreign minister defected.

He said of course there would be defections among senior members of the regime because some of them are old and tired and "not young like us."

He also dismissed the idea that Koussa might have new information to offer British authorities about the Lockerbie bombing in which he was a key negotiator.

"The British and the Americans ... they know everything about Lockerbie so there are no secrets" Koussa can reveal, Seif said.

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Al-Shalchi reported from Tripoli. Associated Press writers Matthew Lee in Washington, Jane Wardell and Cassandra Vinograd in London and Slobodan Lekic in Brussels contributed to this report.