BRUSSELS (Reuters) - It was always going to be a challenge for Britain and the European Union to meet an end-of-year deadline to agree on their post-Brexit relationship.

But the coronavirus has just made it even harder, and calls for an extension to the deadline are gaining traction in mainland Europe as parts of the continent go into lockdown.

Talks planned for this week have been postponed because of the outbreak, and the EU’s chief negotiator, Michel Barnier, said on Thursday he has the COVID-19 respiratory illness that the coronavirus can cause.

“I tested positive for COVID-19 yesterday,” Barnier said in a video message from his home in France where he is now confined. He also issued a rallying cry for fellow Europeans to “win this collective battle, this war, against the virus.”

Barnier last met British Brexit negotiator David Frost in person in the first week of March, during the first round of talks after Britain formally left the EU on Jan. 31.

Britain is now in a transition period where EU rules on trade, travel and business continue to apply until Jan. 1 next year. The talks with the EU are meant to reach agreement on subjects from trade to security cooperation EU by then.

But since the last talks, the coronavirus outbreak has worsened in Europe and national economies have been hit as the death toll rose and countries went into lockdown.

FILE PHOTO: Michel Barnier, Brexit chief negotiator for Europe on future ties with Britain, speaks during a news conference after the first week of EU-UK negotiations, in Brussels, Belgium, March 5, 2020. REUTERS/Johanna Geron

EU diplomats and officials say increasingly in private that they do not see how agreement can be reached by the end of this year. But governments are reluctant to say this in public for fear of being accused of using it as a negotiating tactic to put pressure on Britain to compromise.

“In a situation with major healthcare challenges in the short- and long-term and economic challenges already requiring urgent action, there will not be enough political time and attention to successfully conclude this EU-UK agreement,” said Fabian Zuleeg of the Brussels-based European Policy Centre think tank.

“The only appropriate answer to this severe challenge both the UK and EU are facing is to delay the negative impact of Brexit by extending the transition period,” he said in a note this week, calling for an extra year until the end of 2021.

JOHNSON STANDS BY DEADLINE

British Prime Minister Boris Johnson has ruled that out, and Britain now has laws enforcing the break with the EU.

“There’s legislation in place that I have no intention of changing,” Johnson said on Wednesday, adding that Brexit was not even being regularly discussed at the moment because of the coronavirus.

Under arrangements between Britain and the EU, London would have until June to ask for an extension, and it would be possible for a maximum of two years.

If no deal is reached by the end of this year, Britain will face the prospect of having to pay into the EU’s new joint budget for 2021-27, something it wants to avoid.

The European Commission, the EU executive, said on Thursday negotiations would carry on despite the coronavirus. The sides have exchanged draft legal texts containing their proposals for how relations should work after the transition period, it said.

Asked about the implications of Barnier’s illness, a spokesman for Johnson said: “We have been in close conversation with the EU about looking at ways to continue progressing the negotiations.”