The First Minister is expected to raise the dispute over funding for rail electrification in the South Wales Valleys at a meeting in London. Carwyn Jones will attend a session of the Joint Ministerial Committee which brings together the UK Government with leaders of devolved governments.
These meetings, which are chaired by the Deputy Prime Minister Nick Clegg, take place regularly and usually cover a wide range of topics that are causing tension between the governments.
I'd be amazed if Carwyn Jones didn't seize the opportunity to return to the disagreement which has soured relations between ministers in Cardiff and London more than any other previous dispute.
The Welsh Secretary David Jones says the Welsh Government must stand by an agreement to fund Valley Lines electrification
The Welsh and UK Governments are arguing over who should pay the bill for rail electrification in the South Wales Valleys