BRUSSELS — A potential dramatic return to Brussels of one of the European Union’s biggest beasts could trigger a massive escalation in the simmering battle for influence between the European Commission and the bloc’s foreign policy wing.
Martin Selmayr — the most powerful person in the EU machinery during the term of former Commission President Jean-Claude Juncker, but who fell out of favor when Ursula von der Leyen took the helm — is in pole position for a newly created senior position inside the European External Action Service, according to two EU officials and one senior diplomat.
While it’s not certain he will get the job, many officials have been talking up his chances. It would mean him working under the EU’s foreign affairs chief Kaja Kallas, whose team, according to officials inside the Commission and the EEAS, already has a fragile relationship with von der Leyen’s office.
The prospect of seeing Selmayr return to Brussels in such a crucial role — offering Kallas the benefit of his German political weight and insider knowledge when negotiating with member countries — is stirring unease inside von der Leyen’s Commission and in some embassies, where officials and diplomats fear it could exacerbate tensions.
“Member states are worried that a nomination of Selmayr could further strain relations between EEAS and Commission,” said one senior EU diplomat.
As Juncker’s chief of staff between 2014 and 2018, Selmayr’s outsized influence and brash personal style earned him the moniker “Monster of the Berlaymont,” a tongue-in-cheek reference to the building that houses the Commission in Brussels. His potential new role could set him up as an alternative power base to von der Leyen, a fellow German conservative, but who isn’t a natural ally ― and her chief of staff Bjoern Seibert.
If approved for the job, which comes with the title “deputy secretary-general for geoeconomics and interinstitutional issues,” Selmayr would be in charge of managing relations between the EEAS and other European institutions, as well as sitting in on meetings of EU ambassadors, known as Coreper, according to a job posting obtained by POLITICO, so he would be back at the heart of decision-making.
‘Overstretched the limits of the law’
In EU diplomatic circles, Selmayr’s potential reemergence is the talk of the town. One national delegation spent the day discussing it, a diplomat said. But they reached the conclusion that Brussels was only big enough for one titan, and that Seibert would find a way to block it.
Selmayr was fast-tracked to the position of Commission secretary-general in 2018, a move the European Ombudsman described as “maladministration” and “stretched and possibly even overstretched the limits of the law.” When von der Leyen became president, Selmayr served in several diplomatic roles including his current job as the EU’s envoy to the Vatican.
“Selmayr did not work out so well the last time he was SG [secretary-general],” a Commission official said, referring to criticisms about his controversial appointment and also how he exerted power.
By bringing Selmayr onto her team, Kallas would get the benefit of a Brussels insider deeply connected to the town’s German conservative power structure. An added benefit for her would be that as a serving EU diplomat, Selmayr would, formally, be loyal to her and the EEAS rather than the Commission — a key advantage over other candidates for the job.

Conservative power structure
Teaming up with Kallas could prove a headache for von der Leyen. The Estonian is known for her outspoken style and headline-grabbing comments that sometimes rub national diplomats, and the Commission, the wrong way.
During a recent interview in New York, Kallas told POLITICO that U.S. President Donald Trump should be doing more to help Ukraine in its war against Russia — a comment that clashed with von der Leyen’s much more cautious language when dealing with the American leader.
In other cases, tensions are less over substance than who gets to take credit for major announcements. When von der Leyen unveiled trade measures and sanctions against Israel during a speech in September, top staff at the EEAS were unaware that the announcement was coming, according to two EU officials, despite the fact that the proposals were based on plans from Kallas’ office.
Known as a hawk on Russia, Kallas irritated some member countries early in her term, which started in December, when she floated a plan to source $20 billion in arms and ammunition to Ukraine without prior consultation with national diplomats. The idea, which had not been vetted by Commission leadership, proved unsuccessful as countries made individual contributions rather than paying into a common EU fund for Ukraine.
A Commission spokesperson did not reply to a request for comment. A spokesperson for Kallas declined to comment. Selmayr declined to comment on “speculation.”
Jacopo Barigazzi and Sarah Wheaton contributed to this report.