The UK Minister for Transport Theresa Villiers will visit the Welsh Assembly today to discuss rail electrification plans for Wales.
But on this visit, she isn't expected to meet Welsh Transport Minister Carl Sargeant.
Plans to electrify the Great Western Mainline as far as Cardiff were announced by the UK Government last year.
But today's talks will focus on the second stage of the project - extending the electric line further West to Swansea and the Valleys.
David Cameron committed to electrifying the Swansea and Valleys line during a local election campaign visit to Barry in April.
Mr Cameron told ITV Wales' Political Editor Adrian Masters:
The cost of the electrification plan is estimated to be up to £450 million pounds.
Simon Hart, MP for Carmarthen West and South Pembrokeshire, told the House of Commons that 'the electrification of the South Wales railway line will cost less than what's being spent on a single Underground station.'
He made the statement to Foreign Secretary William Hague, who was standing in for David Cameron, during Prime Minister's Questions yesterday.
"Wales is the only nation in the UK without a single yard of electrified track. Will you put pressure on the Government to electrify the line not only to Cardiff but to Swansea?" asked Mr Hart.
"This would not only be good for jobs in Wales, but would also cost less than the current refurbishment of Tottenham Court Station."
William Hague said that a final announcement on the electrification project would come shortly.