This week's EU summit in Brussels has been cancelled after European Council president Charles Michel reported that a security officer, with whom he had been in contact last week, has tested positive for Covid-19.
The meeting will now take place on 1-2 October.
The Taoiseach, Micheál Martin, was due to attend the summit, which was due to address the EU's Covid recovery fund, as well as the recent repression in Belarus.
The news was announced via the Twitter account of Charles Michel's spokesperson Barend Leyts.
Mr Leyts said: "The @eucopresident today learned that a security officer, with whom he was in close contact early last week, tested positive for COVID.
"The President is tested regularly and test negative yesterday.
"Respecting Belgian rules, he has gone into quarantine as of today."
European leaders and ministers have resumed face-to-face meetings under social distancing rules, but EU officials in Brussels still abide by Belgium's lockdown rules imposed to battle the pandemic.