Two days of strikes on Scotland's rail services will go ahead this week after talks aimed at averting the action broke down today.

Network Rail signalling workers will walk out at noon tomorrow on the first of two 24-hour strikes, with the second starting at noon on Thursday.

A row over staff rosters is at the heart of the dispute.

Rail Maritime and Transport (RMT) union officials met Network Rail managers today but failed to find a resolution.

Network Rail said it was "bitterly disappointed" at the prospect of strikes.

Eight hours of talks were held at conciliation service Acas in Glasgow on Friday but ended without resolution, and the two sides reconvened today.

David Simpson, Network Rail route director in Scotland, said: "Despite our best efforts to resolve this dispute during our talks with Acas today and on Friday, we are bitterly disappointed to inform passengers and freight operators that the RMT still intends to take strike action this week.

"We have been unable to shift the union from their position - a position that puts safety at risk by demanding safety assessments be voluntary, not compulsory.

"We have prepared a contingency train service which aims to reduce the impact on passengers as far as possible.

"Details are available from train operators and National Rail Enquiries."

Network Rail said it has no intention of changing the established principle that rostered hours are binding.

The RMT said Network Rail wants to make changes to rostered hours but the company claimed this was untrue.

About 450 members of the RMT union in Scotland will take part in the strikes.

First ScotRail said last week there will be severe disruption if the strikes are not averted.

It said services would have to wind down after the morning peak on Tuesday and Thursday and there would be reduced frequency and capacity on routes where services are provided.

Mary Grant, managing director of First ScotRail, said: "We will be disappointed if the dispute is not resolved and apologise in advance to all who would be affected and inconvenienced by a strike which is outwith our control."