Mark Rutte has moved a step closer to becoming the next secretary general of Nato after Estonian prime minister Kaja Kallas, seen as one of his main potential rivals, endorsed his candidacy.

In a social media post on Tuesday, Kallas said she was satisfied after talking to Rutte that he was committed to Nato’s priorities, including deterrence, defence spending and Ukraine’s future membership.

Kallas was never an official candidate for the post, but was seen as one of the strongest contenders, especially as many countries in central and eastern Europe have argued that the region is underrepresented. The only other declared candidate is Romanian president Klaus Iohannis.

For a strong #NATO, we need to be clear-eyed on Russia, boost deterrence and defence spending, back Ukraine’s membership, and geographic balance.

I have discussed this in depth with @markrutte and he commits to these priorities. Estonia can back him for NATO’s Secretary General.

— Kaja Kallas (@kajakallas) April 2, 2024

Last month Kallas queried Rutte’s commitment to Nato during his 14 years as prime minister, when the Netherlands never achieved the alliance’s target of spending 2% of GDP on defence.

Lithuania is also understood to be backing Rutte, giving him the support of 28 out of the 32 Nato members.

The United States has made no secret of the fact that it favours Rutte as the successor to Jens Stoltenberg, who is stepping down in October. It wants the next secretary-general to be nominated in time for the July summit in Washington.

At a press briefing on Tuesday, Julianne Smith, the US permanent representative, said: “We fully back Mark Rutte as the next Secretary General, but we do have deepest respect for our friend President Iohannis as well and we appreciate him throwing his hat in the ring.”

Hungary stalling

The strongest resistance is likely to come from Hungary, following Rutte’s public criticism of Victor Orban’s track record on the rule of law, and Turkey.

Turkish president Recep Tayyip Erdogan wants Nato to pay more attention to threats from terrorist organisations and the interests of non-EU nations.

He also clashed with Rutte in the run-up to the general election in 2017 when foreign minister Mevlüt Çavusoglu’s plane was banned from landing in the Netherlands, where he was due to address a rally of Turkish voters during a separate referendum campaign.

If Rutte is appointed before negotiations to form the next Dutch cabinet are concluded, the VVD party will have to nominate an interim prime minister to take his place, which would be an unprecedented move.