SHANNON, Ireland (Reuters) - The United States wants the terms of Britain’s exit from the European Union to protect stability on the island of Ireland and respect Northern Ireland’s 1998 peace deal, U.S. Vice President Mike Pence said on Monday.

FILE PHOTO: U.S. Vice President Mike Pence delivers a speech during a commemorative ceremony to mark the 80th anniversary of the outbreak of World War Two in Warsaw, Poland September 1, 2019. Dawid Zuchowicz/Agencja Gazeta via REUTERS

A proposed clause in Britain’s EU divorce deal designed to protect the peace deal by ensuring an open border between Ireland and Northern Ireland has become the key sticking point in efforts to agree a managed exit before Britain’s exit date of Oct. 31, raising fears of a chaotic withdrawal.

British Prime Minister Boris Johnson has demanded that the so-called “backstop” clause be removed as it could subject Britain to EU rules after exit day, but the Irish government says that can only happen if an alternative mechanism to ensure an open border is agreed.

“We will continue to work closely with our partners in Ireland and the United Kingdom to support a Brexit plan that encourages stability and also one that keeps the strong foundation forged by the (1998) Good Friday Agreement,” Pence told reporters after arriving in Ireland for a two-day visit.

“We understand these are complex issues,” said Pence after arriving at Shannon Airport from Poland where he commemorated the 80th anniversary of the beginning of World War Two.

On Thursday Pence is due to visit London and meet with Johnson, who U.S. President Donald Trump last week praised as “exactly what the U.K. has been looking for”.

Pence said he hoped talks with the Irish government on this issue would make Washington “even better equipped to hopefully play a constructive role in ensuring that when Brexit occurs it in turn will reflect stability and addresses the unique relationship between the UK and the Republic of Ireland”.

The Good Friday agreement, which helped end three decades of violence in Northern Ireland, dismantled all physical border infrastructure between EU member Ireland and the British province of Northern Ireland, guaranteeing that people and goods on either side can move freely.

U.S. House of Representatives Speaker Nancy Pelosi last month said there was no chance Congress would approve a planned U.S.-British trade deal if Britain’s exit from the European Union undermined the landmark 1998 Good Friday peace agreement.

Pence, a descendent of Irish immigrants, is visiting Ireland for the first time as vice president.