DUBLIN (Reuters) - Ireland is not ruling out seeking special post-Brexit arrangements for itself and Northern Ireland as a fallback option in the negotiations on Britain’s departure from the EU, Prime Minister Leo Varadkar said on Wednesday.

Britain's Prime Minister Theresa May welcomes Ireland's Taoiseach Leo Varadkar to Downing Street in London, September 25, 2017. REUTERS/Hannah McKay

Ireland has proposed that Britain and the EU reach a bespoke customs union partnership to eliminate the risk of a hard border returning between it and Northern Ireland, which will be the UK’s only land frontier with the EU after its departure.

Varadkar said this remained EU-member Ireland’s position in the negotiations being led by Brussels but that it “of course has fallback positions if things don’t work out.”

“We’re determined to secure a customs union partnership and a free trade agreement or area between Britain and Ireland when it comes to the post-Brexit scenario,” Varadkar told parliament.

“We certainly don’t rule out seeking special arrangements for Ireland and Northern Ireland but that’s not our negotiating position or preference by any means.”

The Irish border is one of three formidable issues Brussels wants broadly solved in the first stage of negotiations with Britain before talks on a future trading relationship can start.

It is particularly sensitive given the decades of violence in Northern Ireland, a British province, over whether it should be part of the United Kingdom or Ireland. Around 3,600 people were killed before a 1998 peace agreement.

Fifty-six percent of Northern Irish voters voted “Remain” in the Brexit referendum last year, split roughly between pro-EU Irish nationalists and more eurosceptic pro-British unionists. But both sides fear a re-hardening of the border, with its likely hammer effect on the economy, could reignite violence.

Britain has said there should be no immigration checks or border posts along the 500-km (300-mile) frontier post-Brexit. But Brussels and Dublin say London has failed to explain how it would square this objective with its stated intention to leave the EU’s customs union.

With close trading links to Britain, Ireland’s economy is also widely considered the most exposed in the EU to any future trade barriers, and Varadkar said Dublin did not “want to sacrifice or give up” its free trade with Britain at this stage.

An analysis by Ireland’s finance ministry showed last month that 11 of the 15 EU goods most exposed to Britain are Irish exports, highlighting the extreme vulnerability to Brexit of some Irish firms.

However a special arrangement that kept Northern Ireland in the customs union would raise the prospect of checks being required on goods moving between it and Britain, a proposal firmly opposed by pro-Brexit unionists in the province.

The leader of the Democratic Unionist Party (DUP), which props up the Conservative government in the British parliament, reiterated on Tuesday that there could not be any barriers between Northern Ireland and the rest of the UK.