An empty Westminster Bridge is pictured in front of Britain's Houses of Parliament in central London on April 13, 2020, as life in Britain continues over the Easter weekend, during the nationwide lockdown to combat the novel coronavirus pandemic. -

The U.K. will most likely fail to strike a new trade agreement with the European Union by the end of the year, analysts said, as the coronavirus crisis threatens to derail official trade talks.

Prime Minister Boris Johnson has pledged to conclude a post-Brexit trade deal this year. The U.K., which left the bloc on Jan. 31, is in a transition phase until December. During the transition, it is working to establish trade arrangements with the 27-nation EU.

However, this timeline is now at risk after the two lead negotiators had to isolate due to Covid-19 infections.

"The pandemic has completely taken over the agenda in both the EU and in London, and relegated the Brexit talks to a secondary issue," Constantine Fraser, European political analyst at research firm TS Lombard, told CNBC on Thursday.

"It was always going to be difficult to reach an agreement in the limited time available this year. The pandemic means it will now be impossible."

British and European negotiating teams held a call on Wednesday for the first time since both lead negotiators were forced to self-isolate.

The EU's negotiator, Michel Barnier, tested positive for the virus in March but he has now recovered. The U.K.'s Johnson announced he had also tested positive for the virus last month. He was discharged from hospital on April 12 after three nights in intensive care, and continues to recover.