Talks on the new Welsh government have been delayed while first minister Rhodri Morgan is treated in hospital.
Rhodri Morgan was admitted to Llandough Hospital yesterday suffering from stomach problems. His spokesman confirmed he would be given a heart test today.
The Labour first minister had been due to discuss the make-up of his Cabinet today, after Plaid Cymru agreed a coalition deal on Saturday.
Plaid's national council backed a coalition deal by 225 to 18, the day after the Labour conference passed it by 78 per cent.
Mr Morgan was supposed to meet Plaid leader Ieuan Wyn Jones to discuss the specifics of delivering the new One Wales agenda.
The Welsh assembly Cabinet contains 12 positions and it is thought Mr Morgan will promote at least three Plaid Cymru AMs.
Talks have now been delayed while the 67-year-old first minister recovers in hospital.
Mr Morgan risked losing power after Labour won only 26 seats of the 60-strong assembly in the May election.
He was, however, reelected as first minister and leader of a minority Labour government.
Previous attempts to form a coalition with both Plaid and the Liberal Democrats collapsed. Plaid reconsidered Mr Morgan's offer after their own attempts to enter a rainbow coalition with the Lib Dems and Tories also failed.
Mr Jones will now join Mr Morgan as deputy first minister.
After his party backed a coalition deal on Saturday, Mr Jones said he was "absolutely delighted" to be joined Mr Morgan at the Cabinet table.
He told BBC News he was "very proud to be the first Plaid leader to be taking the party into government".
The Welsh Conservatives tentatively wished the new government well, but warned it would be scrutinising every announcement.
Nick Bourne, leader of the Welsh Conservatives said: "It is absolutely vital that this Labour-Plaid alliance works for Wales, not each other.
"I remain convinced that no matter how hard they try, Plaid Cymru will be dominated by Labour in this new arrangement."
Scottish first minister Alex Salmond sent his congratulations to his fellow nationalist leader.
Mr Salmond said: "Plaid's success underlines the utterly changed political landscape of these islands. As a result of the positive events of the last few weeks in Scotland, Wales and Northern Ireland, there are now seven political parties in government in the UK.
"This diversity is to be welcomed, and also reinforces the case for there to be formal mechanisms for dialogue across the different administrations."
Both Plaid and Labour have now agreed to hold a referendum on plans to give the Welsh assembly enhanced law making powers, in line with the Scottish parliament.