* British PM to address Conservatives' annual conference
* Johnson set to unveil Brexit proposal to EU
* He says UK will leave on Oct. 31, with or without a deal
By Elizabeth Piper
MANCHESTER, England, Oct 1 (Reuters) - Prime Minister Boris Johnson will on Wednesday unveil his final Brexit offer to the European Union and make clear that if Brussels does not engage with the proposal, Britain will not negotiate further and will leave on Oct. 31.
In his closing speech to his governing Conservatives' annual conference, Johnson will stick to his hard line on Brexit, offering the party faithful the first details of what he will describe as his "fair and reasonable compromise".
With less than a month until Britain is due to leave the EU, the future of Brexit, the country's biggest trade and foreign policy shift in more than 40 years, is uncertain. Britain could leave with a deal, without one or not exit at all.
Johnson, who says Britain will leave the bloc on Oct. 31 no matter what, will tell the conference he will send his proposal to Brussels on Wednesday, an attempt to secure a deal to smooth the country's departure and avoid a potentially economically damaging no-deal Brexit.
"My friends, I am afraid that after three-and-a-half years people are beginning to feel that they are being taken for fools. They are beginning to suspect that there are forces in this country that simply don't want Brexit delivered at all," he will say, according to extracts released by his office.
"Let's get Brexit done on October 31 so in 2020 our country can move on."
More than three years after Britain voted to leave the EU in a 2016 referendum, Brexit talks are at an impasse.
Johnson has been firm that the Oct. 31 deadline will be met, but parliament has put roadblocks in his way - passing a law that requires the prime minister to request a Brexit delay if he fails to secure an acceptable deal at an EU summit on Oct. 17.
The EU has repeatedly asked Britain to come up with "legal and operational" proposals for the changes Johnson wants to a deal his predecessor negotiated with the bloc last year.
"NOBODY WILL WORK ON A DELAY"
Following its rejection three times by parliament, Johnson has demanded changes to the Withdrawal Agreement, especially over arrangements for a new border with the bloc between the British province of Northern Ireland and EU member Ireland.
But after weeks of talks since Johnson took power that have made little headway to break the Brexit stand-off, the prime minister will make his last gambit - a new proposal which British officials describe as the final offer.
"The government is either going to be negotiating a new deal or working on no deal — nobody will work on delay," a senior government official said.
"We will keep fighting to respect the biggest democratic vote in British history. The EU is obliged by EU law only to negotiate with member state governments, they cannot negotiate with parliament, and this government will not negotiate delay."
Johnson has made the gamble that by pressing a hardline position on Brexit he will steal votes from parties such as the Brexit Party led by veteran eurosceptic Nigel Farage at an election, widely expected to come before the end of the year.
He also has the main opposition Labour Party in his sights, and will use his speech to attack its leader, Jeremy Corbyn, who has led efforts to try to stop the prime minister taking Britain out of the EU without a deal.
"Can you imagine another three years of this? That is the Corbyn agenda – stay in the EU beyond October 31, paying 1 billion pounds ($1.23 billion) a month for the privilege, followed by years of uncertainty for business and everyone else," he will say.
"That is why we are coming out of the EU on October 31. Let's get Brexit done - we can, we must and we will." ($1 = 0.8123 pounds) (Additional reporting by Kylie MacLellan and William James, Editing by Timothy Heritage)