BRUSSELS (Reuters) - The European Union said on Tuesday talks on post-Brexit ties with Britain would kick off next Monday, but warned that the process would be “very hard” and could fail if London fails to secure the Irish border as previously agreed.

FILE PHOTO: Irish Minister for Foreign Affairs Simon Coveney speaks at the launch of his party's manifesto for the Irish General Election in Dublin, January 24, 2020. REUTERS/Lorraine O'Sullivan

Britain left the EU on Jan. 31 after more than three years of tortuous divorce talks, greatly complicated by sensitivities around the Irish border, the only land frontier between the bloc and the United Kingdom now and with a past history of violence.

With both sides talking tough ahead of the negotiations, Ireland warned that even a basic trade deal would be impossible by the end of this year if London does not honour border obligations under its exit deal.

“If there isn’t progress on the infrastructure needed... in the next few months, that’s going to be a very worrying signal for whether or not it’s going to be possible to conclude something sensible before the end of the year,” Irish Foreign Minister Simon Coveney told reporters in Brussels on Tuesday.

“If that doesn’t happen, it will damage significantly the prospects of being able to get even a bare-bones trade agreement... by the end of the year.”

That message was reinforced by the EU’s Brexit negotiator Michel Barnier, who also said the first round of talks would take place in Brussels from next Monday to Thursday, followed by a second round in London later in March.

The British government said separately it would publish its own negotiating lines for the EU talks on Thursday.

“The UK’s primary objective in the negotiations is to ensure we restore our economic and political independence on Jan. 1, 2021,” Prime Minister Boris Johnson’s spokesman said in a reference to Britain’s status-quo transition period that is due to run till the end of 2020.

Under the complex divorce settlement between the world’s fifth-largest economy and the biggest trading bloc, Northern Ireland remains in the UK’s customs area but tariffs would apply on goods crossing from mainland Britain to Northern Ireland if they were headed further to Ireland or elsewhere in the EU.

“We will comply with our obligations,” a Johnson spokesman said on Monday. “Beyond the limited changes... there will be no changes to Great Britain-Northern Ireland trade and we have not asked any ports to prepare for new checks or controls between Great Britain-Northern Ireland.”

Britain has also said it will not introduce any new checks or controls at the land border with Ireland. Coveney and Barnier stressed the EU would see that as undermining trust between the sides, which they said was crucial for the new talks to succeed.

“The UK cannot have quality access to the (EU) single market if it is not prepared to accept guarantees that competition remains open, free and fair,” Barnier said.

“VERY HARD WORK”

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Coveney and Barnier spoke as the EU’s 27 countries approved on Tuesday the bloc’s joint negotiating mandate.

Britain’s current trade with the EU, in the customs union and single market of which it will remain a member until Dec. 31, is now made up of 45% exports and 53% of imports.

On offer from the EU is trade without tariffs or quotas in exchange for the UK committing not to undercut European companies with lower - and therefore cheaper - environmental, labour, tax and state aid standards.

But Johnson rules out being bound by EU rules.

London says it is ready to accept tariffs and quotas similar to a deal the EU has with Canada, or trade on basic, less-beneficial World Trade Organization rules - which assume tariffs, quotas and cumbersome paperwork - from 2021, should a comprehensive trade deal prove elusive.

“The EU has respected the autonomy of other major economies around the world such as Canada and Japan when signing trade deals with them. We just want the same,” Johnson’s Downing Street office said on Twitter.

Barnier said this was not possible as Britain neighbours the EU and its potential impact on the single market is much bigger. Barnier also said fisheries must be part of any deal.

Dutch Foreign Minister Stef Blok said: “The time pressure is immense, the interests are huge, it’s a very complicated treaty, so it will be very hard work.”