Theresa May will step up her fightback against moves by Conservative MPs to oust her with a hard-hitting speech to business leaders on immigration.
After appearing on Sky News' Sophy Ridge on Sunday, the embattled prime minister's next bid to sell her Brexit deal will come at the conference of the pro-EU CBI in London today.
At the same time, Mrs May and her allies are anxiously waiting to hear if the number of Tory MPs demanding a no-confidence vote has reached the required 48.
The rebellion continued to grow over the weekend with the Tories' former candidate for London mayor, Zac Goldsmith, becoming the latest MP to demand the PM's resignation.
In her Sky News interview, Mrs May said that as far as she was aware the number of letters to the 1922 Committee chairman, Sir Graham Brady, had not yet reached 48.
And in response to demands from the so-called "Pizza Club" of Brexiteer cabinet ministers, led by Andrea Leadsom, she announced she would travel to Brussels this week in a bid to get a better Brexit deal.
Meanwhile, Sky News understands that when Michel Barnier met ambassadors from the remaining 27 this weekend, he suggested the two-year transition period could be extended to 2022 - far longer than the "few months" extension set out by Mrs May when she initially proposed the idea at the EU Council summit last month.
The CBI has backed the PM's Brexit plan and director general Carolyn Fairbairn told Sophy Ridge on Sunday: "I think many of us in business have watched on with a degree of horror, that there's so little sense of consensus.
"It almost feels like there is a Westminster bubble beyond which people are not thinking about the real people in this country who work in manufacturing and will be affected by this."
Looking ahead to her talks with Brussels chief Jean-Claude Juncker, Mrs May will tell the CBI: "We now have an intense week of negotiations ahead of us in the run-up to the special European Council on Sunday.
"During that time I expect us to hammer out the full and final details of the framework that will underpin our future relationship and I am confident that we can strike a deal at the council that I can take back to the House of Commons.
"The core elements of that deal are already in place. The withdrawal agreement has been agreed in full, subject of course to final agreement being reached on the future framework.
"That agreement is a good one for the UK. It fulfils the wishes of the British people as expressed in the 2016 referendum. I have always had a very clear sense of the outcomes I wanted to deliver for people in these negotiations.
"Control over our borders, by bringing an end to free movement, once and for all.
"Control of our money, so we can decide for ourselves how to spend it, and can do so on priorities like our NHS.
"Control of our laws, by ending the jurisdiction of the European Court of Justice in the United Kingdom and ensuring that our laws are made and enforced here in this country.
"Getting us out of those EU programmes that do not work in our interests, like the Common Agricultural Policy and Common Fisheries Policy."
Talking tough on immigration, in a message aimed at Brexiteer Tory MPs, the PM will say: "It will no longer be the case that EU nationals, regardless of the skills or experience they have to offer, can jump the queue ahead of engineers from Sydney or software developers from Delhi.
"Instead of a system based on where a person is from, we will have one that is built around the talents and skills a person has to offer.
"Not only will this deliver on the verdict of the referendum. It should lead to greater opportunity for young people in this country to access training and skilled employment.
"We want an immigration system for the future that everyone can have confidence in. Yes, a system that works for business. One that allows us to attract the brightest and the best from around the world, more streamlined application and entry processes."
Following the PM's CBI speech, Labour leader Jeremy Corbyn will tell the business leaders his party has an alternative Brexit plan.
"The prime minister has negotiated a botched, worst-of-all-worlds deal which is bad for Britain, leaving the country in an indefinite halfway house without a real say," he will say.
"The government is trying to force a bad deal that doesn't meet our country's needs by threatening us all with the chaos and serious damage to our economy of a no-deal outcome.
"The prime minister knows that no deal isn't a real option. Neither the cabinet nor parliament would endorse such an extreme and dangerous course."
Labour's alternative plan would include:
:: A permanent customs union, with no hard border in Northern Ireland and avoiding the need for the government's backstop deal
:: A strong single market relationship
:: Guaranteed workers' rights and protection for consumers and the environment.
And Mr Corbyn will say: "If the Prime Minister is unable to negotiate an agreement that can win a majority in parliament and work for the whole country, Labour's alternative plan can and must take its place."
But there's no let-up from Boris Johnson. In his Daily Telegraph column, he steps up his attack on the Brexit deal, accusing Brussels of "malice" and Theresa May of "tragic illusion" or "deception".
He writes: "Of all the lies that are currently being peddled, the worst is that this agreement can somehow be remedied in the next stage of the talks. I have heard it said that this is like a football match, in which we are one-nil down at half-time..."
And he concludes: "We can turn this round. But we are not one-nil down. We are five-nil down, and if we go on like this the second half will be worse."