Full negotiations had been due to start on June 19, but Brussels said the date was still not confirmed after British Prime Minister Theresa May unexpectedly lost her majority in parliament.
In a sign of the confusion, the furthest the two sides have managed to progress is to have what a European Commission spokesman called "talking about talks" in a bid to move forward.
"We are fully prepared and ready for negotiations to start," commission spokesman Alexander Winterstein told reporters.
"When will be the point from moving to talking about talks, to more detailed talks, I cannot say. This doesn't depend entirely on us."
More From This Section
Brussels has warned that time is running out to start the talks on divorce terms and a future trade deal, with Britain set to leave the EU come what may in March 2019.
London has said it wants formal political talks between Barnier and Brexit minister David Davis to start next Monday but it since Thursday's election it has not formally committed to the date.
Davis told BBC radio Monday that the government stood by its threat to "walk away" with no deal if talks -- when they do eventually start -- break down.
Winterstein said the commission was "quite confident" that so-called technical talks to pave the way for the Barnier-Davis negotiations could begin as early as this week.