Who could be the next leader of NATO?

STORY: Behind closed doors in Europe and North America, in capitals and military headquarters, there's an intense debate unfolding:

Who should become the next leader of the NATO military alliance?

But while Secretary-general Jens Stoltenberg is expected to step down in September, and a replacement could be named as early as July, there are many names being put forward... and no obvious frontrunner.

So, who are some of them, and what's the debate?

Jamie Shea is with the Chatham House think tank in London and a former NATO spokesperson:

"There's no shortage of possible candidates, many women, women's names are being suggested. And as NATO has never had a female secretary-general before, I think in terms of conveying the impression of a 21st century alliance attuned to modern society, it's high time that the secretary-general of NATO should be a woman, as has been the case with so many other international organizations. Of course, countries like in central and eastern Europe that have been in NATO for some time already and are playing a big role in the current collective defense on the eastern flank, they may well feel 'It's our time to have the job as, as well.'"

Diplomatic sources say the names being discussed include Denmark's prime minister, Mette Frederiksen.

She says she hasn't officially applied for the job, but regardless she's emerged as one of the bigger contenders.

At 45, she was the country's youngest prime minister when she was elected and won praise for her crisis management during the COVID pandemic.

But, she'd have to step down as prime minister, which might create political turmoil at home.

And her country's military spending is also well below the 2% of GDP that NATO has as its guideline, although she's said she wants to boost it.

In Eastern Europe, Estonia's Prime Minister Kaja Kallas has been discussed. She's also 45 and was the first woman elected as prime minister there. But some members see Kallas as too hawkish on Russia.

In the United Kingdom, its secretary of defense Ben Wallace has put his own name forward. He's highly respected across the alliance, a member of parliament, and also a former military officer.

But some European Union countries, such as France, want a NATO leader from within the EU.

Many also prefer a candidate that used to be a president or prime minister. Stoltenberg himself is the former leader of Norway.

Diplomats told Reuters that Wallace may be a long shot.

"My sense given the role of NATO today, the importance of NATO today, the allies will be looking for somebody who is a serving prime minister because a prime minister really has the contacts, the address book, the ability to make immediate phone calls to presidents and prime ministers both in the NATO countries and beyond, which are geared to the kind of high level diplomacy that NATO is now carrying out."

There are other names being discussed but there's also another angle: some diplomats predict that many candidates would be deemed unacceptable to NATO members Turkey and Hungary, who are often at odds with the other allies over key issues.

Turkey and Hungary are blocking Sweden's attempt to join NATO right now.

In the end, Stoltenberg may be asked to stay on in his role to keep a united front in the face of war.

TURKISH FOREIGN MINISTRY / REUTERS / ESTONIAN PRIME MINISTER OFFICE / UKRAINIAN PRESIDENTIAL PRESS SERVICE / NATO / EUROPEAN UNION / HOST BROADCASTER POOL / 3rd assault brigade/ Ukrainian Armed Forces Press service / Command of the United Forces of the Armed Forces of Ukraine