Thousands of Pakistani truck drivers Wednesday prepared to resume key NATO supply convoys into Afghanistan as a coalition of religious and banned organisations called for countrywide protests.

Islamabad agreed to reopen the land routes into its war-torn neighbour to end a bitter seven-month standoff after US Secretary of State Hillary Clinton said she was sorry for the deaths of 24 Pakistani soldiers in an air strike in November.

The incident enraged Pakistan, prompting the closure of the supply lines and plunging ties with the United States to a new low, after the US raid to kill Osama bin Laden.

But the country's hardline Islamists, who oppose Islamabad's terror alliance with the US, condemned the deal.

"We will observe the protest day against resumption of NATO supplies on July 6 and hold a long march from Lahore to Islamabad on July 8," chairman of the Defence of Pakistan coalition, Maulana Samiul Haq said.

Briefing the media after the coalition's meeting in the garrison town of Rawalpindi, Haq, who runs an extremist madrassa that educated several Taliban leaders, threatened a blockade if the government does not reverse its decision.

"The coalition will practically block the supplies in the second phase of its protest campaign if the government fails to reverse its decision," he said.

He added that all opposition parties including the main Pakistan Muslim League (Nawaz) and cricketer-turned-politician Imran Khan's Movement for Justice party will also be invited to join hands with the coalition in the march and to a conference on July 7.

The coalition has attracted large turnouts at its recent rallies across the country, that some see as a build up to the formation of a political party to contest Pakistan's next general election, widely expected within the next year.

As part of the re-opening deal, which followed months of negotiations, Washington will release about $1.1 billion to the Pakistani military from a US "coalition support fund" designed to reimburse Pakistan for the cost of counter-insurgency operations.

Islamabad, a key but wary US ally in the fight against Taliban militants, had steadfastly insisted on an apology for the November attack, but Washington had previously only expressed regret.

In the sprawling port city of Karachi on Wednesday, drivers and their helpers were cleaning hundreds of trucks that have stood idle during the seven-month layoff.

Driver Mohammad Hassan, 45, said he was pleased the convoys would resume.

"We were unemployed for a long time. Many vehicles broke down due to prolonged parking. Now we shall have our livelihood again," he told AFP.

"This job is dangerous, but we have to make a living," he said, while urging the government to provide the convoys with more protection.

The deal, formally approved by the full cabinet on Wednesday, drew a swift warning from the Pakistani Taliban, who vowed to attack the trucks and kill the drivers if they resumed ferrying supplies to Afghanistan.

The president of the All Pakistan Oil Tankers Owners Association Akram Khan Durrani said the move would be welcome news for his 10,000 drivers and crew, but he urged the government to take action on security.

"The government should issue a regulation under which all NATO supply vehicles have a different colour and are given security cover, so that other vehicles are not attacked by militants and we do our work without any fear," he told AFP.

Durrani said before the ban there were 5,000 oil tankers supplying Afghanistan, but this figure has fallen to 3,000 after many vehicles were dumped or converted to other uses.

The land routes into Afghanistan are vital as the United States and its NATO allies withdraw troops and equipment built up in Afghanistan since the 2001 invasion.

The blockade had forced the United States and its allies to rely on longer, more expensive northern routes through Central Asia, Russia and the Caucasus, costing the US military about $100 million a month, according to the Pentagon.

At the Torkham border crossing, the main transit point for vehicles travelling into Afghanistan, customs officials were preparing for the influx of vehicles and some officials voiced concerns about about attacks.

"For the moment some 550 security personnel are providing security but we will have to raise their number," Miraj Khan, an administrative official, told AFP.

Initial hopes of a deal on reopening the routes fell apart at a NATO summit in Chicago in May amid reports that Pakistan was demanding huge fees for the thousands of trucks that rumble across the border every year.

Clinton stressed "Pakistan will continue not to charge any transit fee".

The US commander of NATO-led forces in Afghanistan, General John Allen, praised the deal as "a demonstration of Pakistan's desire to help secure a brighter future for both Afghanistan and the region at large".