Bratušek is an experienced politician and as a woman she would get one of the vice-president posts in the Commission, the same source said.

Juncker appears to favour Bratušek as a means of filling the female quota on the Commission, as only three of the 23 countries that have so far nominated their candidates have put forward women, according to unofficial reports.

If Juncker's Commission does not have a sufficient number of women, the European Parliament could reject his team, according to the diplomatic source.

Juncker has been in close contact with all EU leaders, including Bratušek, with the diplomatic source saying the two have spoken on the phone in recent days.

The same source said member states could also nominate several candidates and leave the final choice up to the Commission president, which is exactly what Luxembourg under Juncker as prime minister did for the Romano Prodi Commission.

Juncker had put forward three candidates and Prodi made the final choice, and the option is possible under the EU Treaty.

The news is certain to add fuel to the heated debate in Slovenia about the commissioner nominations, which has been made complicated by the current interregnum.

Bratušek had been mentioned as a likely candidate but the move was labelled as "unhygienic" since it would require that she effectively nominate herself.

Moreover, the likely new prime minister-designate, Miro Cerar, indicated he did not see Bratušek in the role.

It was ultimately agreed that the outgoing government would make the nomination, but with the consent of the election winners.

After weeks of back-and-forth the latest consensus appears to be to simply nominate Janez Potočnik, who has already served two terms on the Commission, but no formal decision has been made yet.

Time for Slovenia is running out as Juncker expects nominations by the end of the month, though he will take the rest of the summer to finalise the team and assign the departments.