LONDON: Britain and Germany on Thursday threw their weight behind Dutch Prime Minister Mark Rutte to become NATO's next secretary general, at a crucial time for the alliance as Russia's war against Ukraine rages on.

Rutte is the frontrunner to replace Jens Stoltenberg, even though a shock win for the far-right at the recent general election in his homeland risks tarnishing his legacy.

UK Prime Minister Rishi Sunak's spokesman said Britain "does strongly back Dutch PM Mark Rutte to succeed Jens Stoltenberg as NATO secretary general".

He said the UK wanted a candidate who would "keep NATO strong and deliver on the alliance's NATO 2030 vision".

Rutte favourite to be next NATO boss despite Dutch vote shock

Rutte, he said, was "well respected across the alliance, has serious defence and security credentials, and will ensure that the alliance remains strong and ready to defend and deter".

German Chancellor Olaf Scholz also supported Rutte, a government spokesman said.

"With his immense experience, his great expertise in security policy and his strong diplomatic skills, he is an outstanding candidate," spokesman Steffen Hebestreit said on X, formerly Twitter.

A successor for Stoltenberg -- who has twice had his decade-long tenure extended -- is expected to be announced before a July summit in Washington.

After ruling himself out for the NATO post in previous years, Rutte told Dutch media in October that running the military alliance was a "very interesting" job and he would be open to the prospect.

Rutte, 57, is currently serving as prime minister in a transitional capacity after far-right leader Geert Wilders scored a stunning Dutch general election win in November.

A familiar figure on the European stage after 13 years as prime minister of the Netherlands, diplomats have already indicated Rutte is favoured by NATO heavyweights Britain and Germany, as well as the United States and France.

But although he has emerged as the clear frontrunner, there are other candidates, including Estonian premier Kaja Kallas and Latvia's foreign minister, Krisjanis Karins.

Some supporters want to wrap up Rutte's nomination soon to avoid the NATO job decision coming too close to European Union top positions, which will be up for grabs after European Parliament elections in June.

There is probably still some haggling ahead, and some analysts say there could be opposition to Rutte from Turkey and Hungary.

One potential stumbling block for Rutte could be the situation he leaves behind in the Netherlands, where Wilders's election victory sent shockwaves across Europe.

If he were to succeed Stoltenberg, Rutte would become the fourth Dutchman to head the NATO alliance.

Stoltenberg told AFP last year that Rutte was a "friend and good colleague".

"He is a capable politician with a lot of experience as prime minister," Stoltenberg said.

"But it's not for me to decide who's going to be my successor."

Rutte's government has taken a prominent role in supporting Ukraine, pledging another two billion euros ($2.2 billion) in November, and in leading the push to give Kyiv F-16 fighter jets.

Supporters insist he is fully aware of the dangers posed by Russia.

His years in power were marked by the killing of 196 Dutch nationals when a missile that investigators say was supplied by Moscow shot down a passenger jet over Ukraine in 2014.

Rutte remains at the helm of the Netherlands while Wilders attempts to revive talks on forming a new government, some three months since the election.

Efforts to form a four-party centre-right coalition broke down earlier in February when one party withdrew in a row over public finances.