An EU flag is seen in front of a UK flag outside the Houses of Parliament in London, Britain, on Jan. 17, 2019.File photo:Xinhua

Britain's chief negotiator David Frost said Thursday that the health of the British and European Union (EU) negotiating teams "comes first" as both sides decided to suspend their post-Brexit talks after one negotiator tested positive for COVID-19.

"I am in close contact with @michelbarnier (EU's chief Brexit negotiator Michel Barnier) about the situation. The health of our teams comes first," Frost wrote on twitter.

"One of the negotiators in my team has tested positive for COVID-19. With @DavidGHFrost we have decided to suspend the negotiations at our level for a short period. The teams will continue their work in full respect of guidelines," Barnier tweeted.

The suspension came after Britain and the EU started a new round of trade talks in Brussels on Monday.

Prior to this week's talks, British Health Secretary Matt Hancock said Monday that the country's red lines remain unchanged and "we're preparing for whatever the outcome is."

Echoing Hancock, a spokesman for British Prime Minister Boris Johnson urged more realism from the EU.

Britain and the EU started their lengthy and bumpy post-Brexit talks in March after Britain ended its EU membership on Jan. 31, trying to secure a future trade deal before the Brexit transition period expires. Serious divergences remain in level playing field, governance and fisheries, among others, after rounds of talks.

Following a phone conversation in early November, Johnson and Ursula von der Leyen, president of the European Commission, said that both sides would "redouble" their efforts.

The two leaders had phone conversations several times instead of face-to-face discussions due to the COVID-19 pandemic. Britain, like such countries as China, Germany, Russia and the United States, is racing against time to develop and try coronavirus vaccines.