Speaking in Downing Street after a meeting of the Cabinet he was unable to say when the Queen would now open Parliament.
The party's only chance of achieving an overall working majority is to partner with the Democratic Unionist Party (DUP), a political outlier from Northern Ireland, which is demanding a package of measures on finance in return for support in Parliament.
However, officials at Number 10 are now hinting it could be delayed, stating that the new leader of the House of Commons, Andrea Leadsom, would provide an update. Ms Leadsom's office made no immediate announcement in response to press queries.
The Queen may have to miss part of Royal Ascot - one of her favourite annual events - if her speech is delayed by a few days.
First Secretary of State Damian Green said: "Obviously until we have that we can't agree the final details of the Queen's Speech".
Brexit Secretary David Davis told BBC Radio 4's Today programme: "We are being given an instruction by the British people and we've got to carry it out".
But after a bruising election result that resulted in a minority government, May can not be sure of getting enough votes in the House of Commons to have the Queen's Speech approved.
UK election result: Theresa May to form government with DUP backing
Already UK bookmakers are slashing the odds of a rival bid, with Boris Johnson once again emerging as a potential front runner. Pro-EU Member of Parliament Anna Soubry brought May's continued leadership into question in her acceptance speech.
Although it is now written on thick goatskin parchment paper, this also needs several days to dry, meaning a speech can not be amended at the last minute.
Pen can not be put to paper until the exact contents of the speech are finalised, which may be dependent on the outcome of Tory talks with the DUP.
Writing in the Belfast Telegraph, she said: "When I meet with the Prime Minister in London tomorrow, I will be mindful of our responsibility to help bring stability to the nation at this time of challenge".
A defeat for its Queen's Speech would be tantamount to a vote of no confidence in the new minority government, it said.
He added: "Any deal which undercuts in any way the process here or the Good Friday Agreement is one which has to be opposed".
Mr Adams also said he hoped Mrs Foster would not get "too mesmerised by what's happening on our nearest off-shore island".
There are reportedly copies of a Conservative majority Queen's Speech and a Labour majority Queen's speech written on the goatskin parchment paper and ready to go, the paper said.
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