As a result, the EU executive's powerful vice-president has become a thorn in the side of a cabinet largely under Ursula von der Leyen's control.

Climate aside, the Spanish socialist has made increasingly bold forays into diplomacy -- most recently this week when she openly distanced herself from the European Commission president.

With strongman politics roiling the globe, von der Leyen made the case Monday for a more "pragmatic", interest-driven foreign policy, declaring: "Europe can no longer be a custodian for the old-world order."

"It is fair to say that maybe it was not the most adequate manner to express herself," Ribera told reporters, before tempering with the assertion von der Leyen was "fully committed, of course, to the international order."

Ribera, 56, has become increasingly assertive in public -- after an initial struggle to make her mark despite a vast brief spanning competition policy and climate action.

"There have been difficult moments," she acknowledged in an interview with AFP. A big setback was the delay of a landmark deforestation law, pushed back twice to end 2026.

- Internal battles -

But she also highlighted successes.

For example, a deal committing the bloc to cut greenhouse gas emissions by 90 percent compared to 1990 levels between now and 2040.

"I'm glad we got there," she said, savouring the moment in her 12th-floor office at the commission in Brussels, after "a complicated discussion".

Policy battles are said to be fierce inside the top team because of what officials describe as von der Leyen's highly centralised management style.

Ribera has butted heads with her boss before, especially over green laws.

She dismissed talk of a rift last year, insisting their relationship was "excellent" despite having "normal" differences of views.

But the vice president has shown she will not back down from a fight.

She has exerted pressure in particular to limit the scope of a proposal that would dilute environmental rules in a bid to help European businesses lagging behind China and the United States.

"Some" might be tempted to "deregulate" the EU and "revert to the past", warned Ribera, who hopes to prevent a dismantling of the bloc's environmental Green Deal faced with pushback from right-wing lawmakers.

Ribera is also well-connected.

"With her background as a minister and in climate diplomacy, she is useful -- having many contacts, particularly at the United Nations," an EU official said.

"It's honourable. She fights for what she believes in."

- Attempt to 'weaken' Ribera -

Critical voices question how impactful she has been.

"Her strategy is almost to act from the outside, to relay the NGOs' message on the Green Deal," a senior European official said, on condition of anonymity. "But that doesn't get her anywhere."

"She has red lines on every issue, so at a certain point, she's no longer listened to," the official added.

One of four socialists in a conservative-led top team, Ribera has been given many responsibilities to juggle -- possibly a calculated choice, some suggest.

Ribera's key remit as EU antitrust chief -- a competence with far-reaching impact -- is a time-consuming one.

In practice this means delegating environmental policy to two more junior commissioners, both from von der Leyen's conservative camp.

"She was given a deliberately large portfolio to weaken her," a commission source said.

- 'Own way' -

But she has earned praise for speaking out on Gaza and other issues.

She called Israel's war in the Palestinian territory "genocide" -- a term the EU refuses to employ.

Ribera likewise denounced "senseless violence" in Minneapolis after two American citizens were killed by federal agents enforcing an immigration crackdown -- whereas the commission called it an "internal" US matter.

Ribera long ago quit Elon Musk's X platform in favour of rival Bluesky -- another way to underscore her independence as US Big Tech heaps pressure on EU regulators.

"Everyone has their own way of expressing themselves," she summed up.