(Adds details of earlier clash, background)
NAFUSA MOUNTAINS, Libya, July 27 (Reuters) - Libyan rebels fighting in the western mountains said on Wednesday they planned to launch a major offensive on the strategic town of Ghezaia near the Tunisian border in the next day or two.
A Reuters correspondent saw at least 20 heavily armed trucks moving in the direction of Nalut, close to the border. Another group of some 30 trucks, camouflaged with mud, congregated further east and were preparing to join the assault.
"We are reinforcing the position around Nalut and we will attack Ghezaia tomorrow or the next day for sure. We plan to take it," Omar Fakkan, a rebel commander, told Reuters.
He said that forces from a number of rebel-held towns in the Nafusa Mountains were gathering in Nalut, ready for the attack.
Another rebel spokesman said earlier on Wednesday that rebels had launched a small attack on Gaddafi's forces in Ghezaia, destroying three tanks. Gaddafi's forces fired Grad rockets at rebel-held Nalut in response but there were no casualties.
Rebel fighters have taken large swathes of the country since the start of an uprising to end Gaddafi's 41-year rule in February and now control much of the Nafusa Mountains, the northeast of Libya and the western city of Misrata.
Yet rebel fighters remain poorly armed and are often disorganised. Despite NATO strikes, they have failed to reach Tripoli and appear unlikely to make a breakthrough before the start of the Muslim holy month of Ramadan in early August.
There was little news of progress on Wednesday on the other fronts near the oil town of Brega or the western town of Zlitan, the largest town separating the rebels from the capital Tripoli.
Hospital sources said four rebels were killed on Wednesday on the front line near Zlitan and 10 wounded. Four rebels were wounded on the front line near Bani Walid to the south west of Misrata.
Reporting by Michael Georgy, Writing by Lin Noueihed, Editing by Roger Atwood