Boris Johnson is updating the cabinet, as UK and EU officials hold talks on getting a deal done in time for the 31 October Brexit deadline.
Commons Leader Jacob Rees-Mogg said “compromise” was inevitable and the PM could be “trusted” to get an agreement acceptable to Leave-backing MPs.
Parliament will meet on Saturday and vote on any deal achieved by Mr Johnson at a Brussels summit this week.
Labour said it would “wait and see”, but would oppose anything “damaging”.
Shadow business secretary Rebecca Long-Bailey told BBC One’s Andrew Marr Show: “We don’t think the Tories have moved too far on on their deal.”
SNP leader Nicola Sturgeon told the same programme: “We will not vote for the kind of deal specified by Boris Johnson.”
Talks in Brussels between UK and EU officials – described as “intense technical discussions” – are continuing on Sunday, while Mr Johnson is briefing ministers by telephone.
Ambassadors to the EU from 27 member countries are scheduled to meet this evening and Michel Barnier, the EU’s chief Brexit negotiator, is expected to brief them on the talks.
The summit in Brussels on Thursday and Friday is seen as the final chance to get a Brexit deal agreed ahead of the deadline of 23:00 GMT on 31 October.
Liberal Democrat leader Jo Swinson told Sky News that any agreement reached by Mr Johnson should “be put to the public so they can have the final say”.
But, asked whether more MPs would be likely to support a deal, if the Commons first voted in favour of putting it to a referendum, Labour leader Jeremy Corbyn said: “I think many in Parliament, not necessarily Labour MPs – others – might be inclined to support it because they don’t really agree with the deal.
“I would caution them on this.”
Home Secretary Priti Patel told the Andrew Marr Show there was much “speculation” about what could be included in a deal.
She added: “Progress has been made by the prime minister.”
Asked about Labour’s stance, Ms Patel replied: “They are clearly playing politics. The British public want to ensure that we get Brexit done.”
Mr Rees-Mogg wrote in the Sunday Telegraph: “In the final stages of the Brexit negotiation, compromise will inevitably be needed, something even the staunchest Leavers recognise albeit unwillingly – but as a Leaver Boris can be trusted.
“He wants to take back control and has dedicated his political career to this noble cause. If he thinks the ship of state is worth an extra ha’porth of tar he deserves support.”
Mr Johnson’s revised proposals – designed to avoid concerns about a hard border on the island of Ireland after Brexit – were criticised by EU leaders at the start of last week.
However, on Thursday, Mr Johnson and Irish Prime Minister Leo Varadkar held talks and said they could “see a pathway to a possible deal”.
The Benn Act, passed by Parliament last month, requires Boris Johnson to ask EU leaders for a delay to Brexit if a deal has not been reached and agreed to by MPs by 19 October.
The first Queen’s Speech of Mr Johnson’s premiership, delivered during the State Opening of Parliament on Monday, will see the government highlight its priorities, including on Brexit.
Timeline: What’s happening ahead of Brexit deadline?
Monday 14 October – The Commons is due to return, and the government will use the Queen’s Speech to set out its legislative agenda. The speech will then be debated by MPs throughout the week.
Thursday 17 October – Crucial two-day summit of EU leaders begins in Brussels. This is the last such meeting currently scheduled before the Brexit deadline.
Saturday 19 October – Special sitting of Parliament and the date by which the PM must ask the EU for another delay to Brexit under the Benn Act, if no Brexit deal has been approved by Parliament and they have not agreed to the UK leaving with no-deal.
Thursday 31 October – Date by which the UK is due to leave the EU, with or without a withdrawal agreement.