BRUSSELS (Reuters) - With few options left to Prime Minister Boris Johnson to achieve his goal of taking Britain out of the EU on Oct. 31, officials in Brussels say that he may need to go back to the idea of a so-called Northern Ireland-only backstop to get a Brexit deal done.

Slideshow ( 3 images )

The contentious backstop - an insurance policy to maintain the sensitive Irish border open under any circumstances after Brexit, including by tying the UK to the EU’s trading and other rules unless another solution is found - has so far proven to be the main stumbling block in the tortuous Brexit talks.

Here is a guide to the latest on the vexed backstop issue.

** The backstop is meant to preserve the seamless border on the island of Ireland - the only future land frontier between the EU and the UK - by having Britain follow the bloc’s rules on trade, state aid, labor and environmental standards so that no checks are necessary.

The EU had initially proposed to apply that mechanism only to Northern Ireland but Britain’s former prime minister, Theresa May, said it would be unacceptable for one of the regions of the United Kingdom to diverge from the rest of the country.

May used to depend on a Northern Irish unionist party, the DUP, for her parliamentary majority and so London demanded that the backstop extend to all of the UK.

** The backstop was a major factor in parliament’s rejection of May’s Brexit deal and Johnson has now made it clear that Britain wants to distance itself from the bloc’s regulations after Brexit. That led the EU to demand protection for its cherished single market from dumping prices and unfair competition that could arise from the open Irish border.

London proposed to Brussels last week that common rules for checking animals and animal products be established across the whole island of Ireland as an alternative to the current backstop that would cover all of the UK.

While that does not address the EU’s demand to ensure fair competition while at the same time avoiding border controls, EU officials and diplomats stress any return to a limited version of backstop increasingly looks like the only possible compromise.

** “What’s there not to like?” a senior EU diplomat said of such a solution, while others stressed that the bloc had previously agreed to such a mechanism and had completed all the legal and drafting work around it, meaning it could be revived swiftly.

The Irish government has said in recent days that it has always been open to a Northern Ireland specific solution to the border.

While the DUP objects to any arrangement that would treat Northern Ireland differently, its voice in the matter has diminished since Johnson has lost his wafer-thin parliamentary majority in the spiraling political turmoil in the UK and so would be short of votes with or without the party.

Brexit watchers in Brussels also see him as less committed to Northern Ireland than May was, especially if delivering Brexit hangs in the balance.

At the same time, however, the bloc is skeptical that any Brexit deal could pass in the current factious UK parliament.