Boris Johnson will update the cabinet later, 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.
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 31 October deadline.
Home Secretary Priti Patel told the Andrew Marr Show there was much "speculation" about what could be included.
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.
Liberal Democrat leader Jo Swinson told Sky News that, although the detail of any deal had yet to be confirmed, it looked "much the free-trade agreement type proposal that was put forward in November 2018 that the government's own analysis showed would be catastrophic".
She added that any deal should "be put to the public so they can have the final say".
Labour leader Jeremy Corbyn said: "I think many in Parliament - not necessarily Labour MPs, others - might be more inclined to support it [if there was a referendum] even if they don't really agree with the deal. I would caution them on this."
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.
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