TRIPOLI (Reuters) - The government of Libyan leader Muammar Gaddafi has contacted foreign states offering an immediate ceasefire, but there was skepticism that the proposal could end the three-month-old conflict.

The ceasefire offer was unlikely to deflect Western leaders, meeting for a Group of Eight summit in the French seaside resort of Deauville, who say they are steadily moving closer to their goal of forcing Gaddafi from power.

Spain said it was one of several European governments to have received a proposal from Libyan Prime Minister Al-Baghdadi Ali Al-Mahmoudi for an immediate ceasefire.

"We've received the message and our position lies with the rest of Europe," a spokesman for the Spanish prime minister's office said.

"Everyone is anxious for there to be an agreement ... but certain steps have to be taken first and so far they haven't been taken," he said.

Foreign reporters in Tripoli were summoned to a news conference given by the Libyan prime minister, though there was no word on what he would be talking about.

Gaddafi's government has offered ceasefires before. Each time, these have been rejected by rebels who say they will accept nothing short of the Libyan leader's departure.

MISRATA MORTAR ATTACK

Despite the latest ceasefire offer, forces loyal to Gaddafi were on Thursday mounting their most intensive bombardment for days in the rebel-held city of Misrata.

A Reuters reporter in the city, which is about 200 km (130 miles) east of Tripoli, said he could hear mortars landing every few minutes in the western outskirts of Misrata.

He said there was a steady flow of ambulances going to and from the front line.

"The bombing started at about 7 a.m. (1 a.m. EDT). Today's mortar fire is quite fierce and sustained. The mortars are coming closer to the front line than they have for several days," said Abdellatif Sueihy, a 56-year-old rebel fighter.

Gaddafi's security forces cracked down ferociously when thousands of Libyans rebelled against his rule. NATO missiles and warplanes have been bombing targets in Libya for two months under a U.N. mandate to protect civilians from attack.

Rebels now control the east of the country, around their main stronghold of Benghazi, and pockets of land in the West.

But the conflict has reached stalemate on the ground, with the rebels unable to advance toward Tripoli and NATO powers -- wary of getting sucked into new conflicts after their experience in Iraq and Afghanistan -- refusing to put troops on the ground.

Nevertheless, Western officials say they are confident that they are gradually loosening Gaddafi's grip on power through a combination of sanctions and military and diplomatic pressure.

"You are wearing down a regime over time," said a U.S. defense official. "You make the elites feel uncomfortable; you get dissension in the upper ranks. It doesn't happen quickly."

"What you are trying to do is get the regime to read the writing on the wall," the official said.

GROUP OF EIGHT

Gaddafi, who has been in power for more than four decades, denies that his troops target civilians and say his security forces were forced to act to put down a rebellion by criminals and members of al Qaeda.

U.S. President Barack Obama said on a visit to London on Wednesday there would be no let-up in the pressure on Gaddafi to quit.

"I absolutely agree that, given the progress that has been made over the last several weeks, Gaddafi and his regime need to understand that there will not be a let-up in the pressure that we are applying," Obama said.

"We have built enough momentum that, as long as we sustain the course that we are on, that he is ultimately going to step down," he said. "Ultimately this is going to be a slow, steady process in which we are able to wear down the regime."

Obama will be among the G8 heads of state who are expected to discuss ways to break the impasse at their summit in France on Thursday and Friday.

Attempts to build a consensus in the group over Libya may be complicated by Russia, which opposes the NATO bombing.

(Reporting by Joseph Logan in Tripoli, Mohammed Abbas in Misrata, Tracy Rucinski in Madrid and Missy Ryan in Washington Writing by Christian Lowe; Editing by Alison Williams)

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