"This union strongly believes that the pressure of the masses is crucial to forcing government to back down on this blatant extortion," spokesman Tahir Sema said in a statement.

"We will aim to make the tolls uncollectable and force the government and SA National Roads' Agency [Limited (Sanral)] to find more equitable ways to pay for road improvements."

Earlier, it was announced that a meeting between the inter-ministerial committee on e-tolling and Cosatu, chaired by Deputy President Kgalema Motlanthe, would convene again next week.

"The meeting [on Friday] agreed that more time was needed for both parties to consider the proposals on the table," Motlanthe's spokesman Thabo Masebe said in a statement.

Motlanthe led the government delegation and Congress of SA Trade Unions (Cosatu) president Sidumo Dlamini the labour delegations at the meeting at the Union Buildings in Pretoria.

It followed a July 20 consultation.

The IMC had been expected to announce its plans on Friday for implementing e-tolling in Gauteng.

However, Masebe said this would be delayed because the IMC needed time to discuss the issues raised.

Cosatu has mounted a campaign against e-tolling, which it believes is the wrong way to raise money to maintain the country's major roads.

The government's plans to introduce e-tolling in Gauteng have provoked opposition by motorists and residents of South Africa's economic heartland.

Sema said the government should scrap the e-toll project.

"Government must investigate as to who was responsible for steam-rolling these projects past all the relevant processes. This, for us, is highly suspicious, given the amounts of money involved in the various toll road projects."

The Opposition to Urban Tolling Alliance (Outa) said it was clear the government intended to launch e-tolling in Gauteng before a court review took place.

This was judging by the comments made by the transport minister urging the public to buy e-tags this week, it said in a statement.

Outa was expecting the IMC to announce it was reducing the e-toll tariff and the capped maximum charge.

Chairman Wayne Duvenage said: They [will] go on the charm offensive to woo the public into believing this is the best option.

"We also believe their announcement will include the acceptance of e-tolling by a few entities that were originally opposed to the plan."

Outa rejected e-tolling under the "user-pays" principle.

Cliff Johnston of the SA National Consumer Union said the collection costs and the burden placed on society were independent of the amount charged per kilometre.

Road users would still have to foot a bill of more than R1.1 billion a year just to cover the electronic toll collection process.

Automobile Association spokesman Gary Ronald said it was worrying that the ETC [Electronic Toll Collection] contracts remained confidential. They should be made public for the citizens who would be paying the toll fees.

The Justice Project SA said it supported Outa.

"JPSA... remains vehemently opposed to this ludicrously costly and inefficient way of collecting funding and paying for infrastructure in our country, effectively privatising public roads and enriching Austrian-based Kapsch TrafficCom," chairman Howard Dembovsky said in a statement.

There was a risk that the e-toll fees could escalate out of control as had happened with other state-owned enterprises, such as Eskom, he said.