The PM said "significant" work was needed, after key figures conducted talks in Brussels over the weekend ahead of Monday's Queen's Speech.
The European Commission said that there have been "constructive technical-level" talks with the UK, though added there was still a "lot of work" to be done to reach a Brexit agreement.
In a statement, the commission said the EU's chief negotiator Michel Barnier had briefed the ambassadors of the remaining EU 27 on the talks.
He said he would be speaking to the European Parliament's steering group and added: "A lot of work remains to be done. Discussions at technical level will continue tomorrow."
It comes after the PM briefed the Cabinet on progress in the negotiations in Brussels in a conference call on Sunday.
A Number 10 spokesman said: "The Prime Minister updated Cabinet on the current progress being made in ongoing Brexit negotiations, reiterating that a pathway to a deal could be seen but that there is still a significant amount of work to get there and we must remain prepared to leave on October 31."
Mr Johnson has steadfastly reiterated his pledge that he will make sure Brexit happens by the October 31 deadline.
On Sunday, the Sinn Fein president and Mr Johnson spoke over the phone to discuss Brexit.
Ms McDonald's office said she reminded the Prime Minister of his obligations under the Good Friday Agreement and told Mr Johnson that there could be no unionist veto on protections for Ireland.
He has previously said he believes there is "a way forward for a deal that could secure all our interests, respect the Good Friday Agreement, get rid of the backstop and get Brexit done by October 31".
Meanwhile, the first Queen's Speech of Mr Johnson's time as PM will be delivered on Monday.
The Government said the Queen's Speech will outline 22 Bills and it is expected to have a major focus on Brexit.
But despite that, Mr Johnson has been keen to focus on his domestic agenda, previously promising a Queen's Speech that will "get this country moving again".
"The people of this country don't just want us to sort out Brexit," he said.
"They want their NHS to be stronger, their streets safer, their Wifi faster, the air they breathe cleaner, their kids' schools better-funded - and this optimistic and ambitious Queen's Speech sets us on a course to make all that happen, and more besides.
"After one of the least-active parliaments in living memory, the proposals we are bringing forward will get this country moving again.
"This is a Queen's Speech that will deliver for every corner of the UK and make this, once again, the greatest place on earth."
The measures include a new Environment Bill setting legally binding targets to reduce plastics, restore biodiversity, improve water quality and cut air pollution.
There will also be Brexit-related legislation intended to establish a "fair" immigration system, ensure faster access to new medicines and to open up markets.
The PM is also expected to use the address to announce proposals for the "revolutionary reform" of Britain's railways.
It is believed this includes proposals to scrap the rail franchising system, the contracting out of services introduced when the rail system was privatised in the 1990s.