(Adds Commission, Lamberts, fresh quotes, other detail)
BRUSSELS, Oct 2 (Reuters) - Britain's latest Brexit proposal was bound for a cool reception in the European Union but the bloc stressed it would examine it in detail as both sides seek to sidestep blame over the increasingly intractable divorce.
On Wednesday, Britain submitted its latest ideas on how to unlock a divorce deal with the EU before Oct.31, when British Prime Minister Boris Johnson has promised to take his country out - with or without an accord to manage the fallout.
Officials and diplomats dealing with Brexit in Brussels said earlier in the day that the proposals, as reported by media, fell flat. Nevertheless, the bloc's executive European Commission avoided dismissing them too early in public.
"We want to look at it objectively. We want to enter into constructive discussions," spokeswoman Mina Andreeva said.
With the EU still left wondering whether Johnson was truly seeking an agreement or just trying to create a semblance of negotiation to then blame it if and when it fails, the bloc was cautious.
"We are going to examine the text," a senior EU diplomat told Reuters.
"We won't blow this out of the water but we are going to subject it to the most rigorous analysis. Either this is a negotiation or it isn't. If it is we will examine this proposal rigorously, and in light of extremely important criteria."
Britain is seeking intensified and entirely secret talks with the EU on its latest proposal, which Johnson's Brexit negotiator David Frost delivered to it on Wednesday.
But, behind the officially constructive tone, there is very little hope left in the EU that a deal can be had with London - and ratified by the factious British parliament - before the Oct.31 deadline.
"The proposal is fundamentally flawed," a senior European Union official said earlier in the day.
An EU diplomat dealing with Brexit said separately that the London plan "won't fly".
They added that heavyweights France and Germany would not press Ireland to accept a proposal being offered by Britain that would affect its currently open border with Northern Ireland.
With the EU determined to avoid any abrupt, no-deal split later this month, EU sources saw another delay to Brexit as increasingly likely.
The 27 EU member states staying on together would not reject a request from Britain to that end because they would not want to be held responsible for any ensuing tremors.
"If they want to commit a stupidity it should be fully their responsibility," the official said. "The EU will never push the UK out, the Union will never close the door."
The tension raises the stakes before an Oct.17-18 summit of EU leaders at which London hopes to seal a new deal and leave two weeks later.
Johnson wants to change a Withdrawal Agreement that his predecessor Theresa May had negotiated with the bloc but which then failed three times in the British parliament.
He wants to strike out the so-called backstop, or emergency arrangements to uphold the open border between the British province of Northern Ireland and EU member Ireland after Brexit, when border checks would become necessary.
So far, Britain's ideas on alternatives to achieve these conflicting goals have failed to convince the EU. The bloc says any change must satisfy the same objectives as the backstop.
These are: maintaining a fully open border between Northern Ireland and Ireland, protecting the EU single market, and maintaining the north-south cooperation made possible by the 1998 peace deal that ended three decades of conflict.
"The remaining options are the original, Northern Ireland-only backstop with some modifications, or an extension," said the diplomat.
The bloc sees the sole possible deal around effectively keeping Northern Ireland - but not the rest of the United Kingdom - in the EU's trade orbit by drawing a border across the Irish Sea.
Johnson has ruled out the Northern Ireland-only backstop idea both publicly and in private.
An EU lawmaker dealing with Brexit said after the British premier's speech on Wednesday: "We are confronted with a prime minister whose strategy, I think, is to achieve a no-deal Brexit and blame EU 'friends' for the unsuccessful outcome." 1/8nL5N26N3FJ (Additional reporting by Clement Rossignol and Jorrit Donner-Wittkopf, Editing by Angus MacSwan)