Guardiola was scheduled to talk to the media ahead of the Premier League leader’s match at Newcastle on Sunday.
Half of the scheduled weekend matches have already been postponed because of COVID-19 outbreaks at clubs, underscoring the worsening health emergency in Britain as the omicron variant spreads.
Guardiola attended Sergio Aguero’s retirement announcement in Barcelona on Wednesday and is now awaiting the result of another test.
The latest postponements brought the total number of top-flight games called off this week to nine.
The league has already reintroduced emergency measures — more frequent testing and wearing face masks indoors among them — but said its intention was to maintain the current schedule “where safely possible,” even as some managers called for a brief suspension in play.
The league said its board was assessing applications to postpone matches on a case-by-case basis.