"The UK strongly backs Dutch PM Mark Rutte to succeed Jens Stoltenberg as NATO Secretary General. Rutte is 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," said the official, speaking on condition of anonymity.

A successor for Stoltenberg -- who has had his decade-long tenure extended twice in the face of Russia's war on Ukraine -- is expected to be announced before a July summit in Washington.

After ruling himself out for the NATO post in previous years, Rutte, 57, in October told Dutch media that running the alliance was a "very interesting" job and he would be open to the prospect if it came his way.

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

Wilders said last week he had asked a new official to revive talks on forming a Dutch government, almost 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.