European Commission chief Jean-Claude Juncker said Britain's planned departure from the European Union was "not an amicable divorce" but called for it to be quick.
"I do not understand why the British government needs until October to decide whether to send the divorce letter to Brussels," he told German public broadcaster ARD late Friday.
"I'd like it immediately."
He admitted that the EU had hoped Britain would stay but that now it was key to make the separation process as speedy and painless as possible.
"It is not an amicable divorce but it was also not an intimate love affair," he said.
"It is not a good day for Britain and the European Union but we must go on."
British Prime Minister David Cameron said Friday in the wake of the shock referendum outcome that he would resign his office by October and leave negotiations on the so-called "Brexit" to his successor.
European Parliament President Martin Schulz, also speaking to ARD, called Cameron's decision to possibly wait until October to leave "scandalous", saying that he was "taking the whole (European) continent hostage." (AFP)