Theresa May is seeking "further clarification" to satisfy MPs after "robust" exchange with EU chief.
Britons will not need a visa but will have to apply for a travel document, which lasts for three years.
MPs may end up backing a new referendum "if none of the other options work", the former PM says.
Rebecca Evans and Eluned Morgan are promoted to cabinet while Alun Davies is sacked.
Jeremy Corbyn is being urged to call a no-confidence vote in the PM by other opposition parties.