The Queen’s Speech – in which the government sets out its legislative programme – has been delayed for a few days, the BBC understands.
The set-piece event had been due to take place on Monday 19 June.
The Conservatives are negotiating with the Democratic Unionist Party to get support for their minority government after losing their Commons majority in last week’s general election.
Labour said the delay showed the government was “in chaos”.
The Queen’s Speech is written by the government and presents an outline of its planned legislation for the next Parliamentary session.
BBC assistant political editor Norman Smith said the decision to delay it revealed an “ambiguity” about what would go in it – with several manifesto pledges expected to be watered down or dropped – but also the need for the Tories to “nail down” DUP support.
A defeat for its Queen’s Speech would be tantamount to a vote of no confidence in the new minority government, he said.
One of the reasons for the delay is also believed to be because the speech has to be written on goat’s skin parchment paper, which takes a few days to dry – and the Tory negotiations with the DUP mean it cannot be ready in time.
Theresa May will face questions later from her backbenchers for the first time since Thursday’s election.
They are expected to raise concerns about her leadership style, and press for more details on talks with the DUP.
Mrs May’s new cabinet is also meeting for the first time after a reshuffle.
Earlier Brexit Secretary David Davis predicted some parts of the Tory manifesto would have to be “pruned” following the election result.
Speaking on BBC Radio 4’s Today programme, Mr Davis said that while the Tory election campaign had been disappointing, Mrs May was a “formidable prime minister” and accused people speculating about her leadership of “the absolute height of self-indulgence”.
But Labour leader Jeremy Corbyn has accused Mrs May of “squatting” in No 10, telling the BBC’s Andrew Marr Show on Sunday that the country “cannot go on with a period of great instability”.
On Sunday evening the PM finalised her cabinet with a small reshuffle, with Michael Gove returning to a ministerial role as environment secretary.
Mr Gove, who took on Mrs May for the party leadership after David Cameron quit, was sacked by the PM in her reshuffle in July last year.
The Conservatives went from 331 seats to 318 in the general election, while Labour increased its number of MPs from 232 to 262.
BBC political correspondent Iain Watson said the meeting with the committee of Tory backbench MPs had been brought forward by 24 hours, not because of panic within the party, but possibly as a way of avoiding it.
One MP told him: “The wise heads will need to tell any hotheads to calm down.”
The 1922 Committee is made up of all Conservative backbenchers – the name is taken from the year in which its original members were elected.
Its primary function is to keep the leadership of the party informed of the mood among the rank and file, and if a Conservative leader or other senior figure loses its support they could be in a particularly vulnerable position.
Graham Brady, chairman of the committee, told BBC One’s Sunday Politics there was “zero appetite” among the public for another election.
A number of high-profile members kept their posts in Sunday’s cabinet reshuffle, with Philip Hammond staying at the Treasury, Boris Johnson remaining at the Foreign Office and Amber Rudd keeping the Home Office brief.
But some changed jobs too, with Liz Truss being demoted from justice secretary to become chief secretary to the Treasury.
Damian Green, who was work and pensions secretary, has been promoted to become the first secretary of state – effectively Mrs May’s second in command.
Analysis by BBC political correspondent Iain Watson
Widespread demands for Mrs May to go are not expected at Monday’s 1922 Committee meeting.
Instead, there will be demands for her to consult more, including meeting regularly with the 1922 executive, and to turn Downing Street from a bunker into an open house by broadening her range of staff.
However, few MPs expect her position to be strong and stable for the next five years.
One senior backbencher told me: “It is inconceivable she will lead the party into the next election. Her authority has been diminished unquestionably.”
Another said: “Party members have been too bruised by her.”
“She has bought herself some time”, said another senior backbencher, but added: “How she behaves will determine how long she’s there.”
There is a feeling that the party is holding on to nurse for fear of something worse.
Johnson: MPs should get a grip
After speculation in the Sunday newspapers that he was mounting a leadership challenge, Mr Johnson has called for Tory MPs to back Mrs May.
Writing in Monday’s Sun, the foreign secretary said those calling for the PM to step down should “get a grip”, adding the electorate wanted the government to “get on with the job”.
Mr Johnson admitted the prime minister’s election campaign did not go well – “to put it mildly” – and that Tory messages “got lost or misunderstood”.
But he added: “Theresa May led a campaign that inspired 13.7m people to vote Conservative, in the biggest total tally of Tory votes since the days of Margaret Thatcher.
“That is a stunning achievement, for which she deserves the support of her party. And she will certainly get it from me.”
He also said the proposal of a deal with the DUP to keep her minority government in power was “feasible”.
“The people of Britain have had a bellyful of promises and politicking,” he wrote.
“Now is the time for delivery – and Theresa May is the right person to continue that vital work.”
Michael Gove’s ‘surprise’
The return of Mr Gove to the front bench as environment secretary has been a shock to some, including the politician himself.
Speaking to Sky News on Sunday, he said he had been “quite surprised” to be asked to rejoin the cabinet.
He added: “Of course I knew that today was reshuffle day, but I genuinely didn’t expect this role – although I am delighted to be part of the government, and delighted to be able to support Theresa.”
However, the BBC’s environment analyst Roger Harrabin said green campaigners were angry at Mr Gove’s appointment, pointing to his time as education secretary, when he tried to remove climate change from the geography curriculum, and as chief whip, when he blocked the then environment secretary from important international talks.
Green Party co-leader Caroline Lucas said: “It is hard to think of many politicians as ill equipped for the role of environment secretary as Michael Gove.”
But others have welcomed the new minister.
One senior farming industry source said they were happy that a “big hitter” was taking the top job at the Department for Environment and Rural Affairs (Defra).
“Defra has long been a backwater, so at last it’s not someone in charge who is being put out to grass,” he said.