Libyan rebels said they had captured part of the oil town of Brega today while their forces in the west pushed toward Zawiyah, trying to get within striking distance of Muammar Gadafy's capital.
Col Gadafy is clinging to power despite a near five-month Nato air campaign, tightening economic sanctions, and a lengthening war with rebels seeking to end his 41-year rule.
The rebels have seized large swathes of the North African state, but are deeply divided and have yet to march on Tripoli.
Today, they reached the village of Bir Shuaib, some 25 km (15 miles) from Zawiyah, which has unsuccessfully risen up against Col Gadafy twice this year. It lies less than 50 km west of Tripoli, on the main road to Tunisia, which has been a lifeline for Libya but has begun to crack down on rampant smuggling.
"We've gone past Nasr village and right now we're about 25 km from Zawiyah," said Faris, a rebel fighter. Rebels prevented reporters from reaching the front to see for themselves.
Rebels in the western mountains do not operate as a single force, as each town has its own command. But when they join forces for major operations they can muster a few thousand men.
Their force is poorly trained and short of heavy weaponry - despite a French arms drop earlier this year - and most analysts do not think they are capable of capturing Tripoli.
On the eastern front near Brega, one rebel spokesman said the opposition had captured the residential districts of the oil town but Col Gadafy's forces still hold western parts of the town where the oil facilities are located.
The residential area where the fighting was taking place is about 15 km east of the oil terminal and sea port.
"It is liberated. It is under our control now," spokesman Mossa Mahmoud al-Mograbi said of the eastern part of the town.
It was not immediately possible for a Reuters correspondent to verify the capture of Brega and rebels have repeatedly claimed to have seized towns in the past, only to be quickly repelled by Col Gadafy's forces.
In an effort to pile economic and military pressure on Col Gadafy, more countries are set to announce next week that they will free frozen assets for the rebels, a British official said.
The senior official said steps taken by the international community meant Col Gadafy and his supporters were nearing a "tipping point" when they would be forced from power.
"While it's hard to predict when this will end, it's easy to see the pressure is building on Gadafy and it is only a matter of time before he's forced to leave power," the official said.
Britain is playing a leading role in Nato air strikes against Col Gadafy's forces, which have weakened his armoury but failed to allow the rebels deliver a knockout blow.
Tightening the economic noose around Col Gadafy, Tunisia said today its troops were patrolling fuel stations to curb the flow of smuggled gasoline into neighbouring Libya.
International sanctions and the effects of Libya's civil war have disrupted normal supplies of fuel to parts of the country under Col Gadafy's control, but huge volumes of gasoline are instead being smuggled across the Libyan-Tunisian border.
The western battle is one of three widely separated rebel fronts against Gadafy forces. In the east around the ports of Misrata and Brega, fighting has been bogged down in recent weeks while the western rebels have advanced.
The two sides have been battling for months over Brega, 750 km east of Tripoli. The rebels see securing the town as a tipping point in the nearly six-month-old war and hope to resume oil exports from there as quickly as possible.