Plans to have a woman leading Nato have been dropped following accusations of former President Donald Trump's misogyny.
There are fears that Trump will cause more damage to transatlantic relations if he returns to the White House.
Jens Stoltenberg, 64, who has had the job since 2014 is set to step down in the spring. His most likely successor is current caretaker Dutch prime minister Mark Rutte.
It is a blow for Estonian PM Kaja Kallas, who was expected to take up the reigns and had hoped to be the first woman and east European ally to hold the top job.
Trump has been criticised for his comments against female world leaders
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During his time as President from 2016 to 2020, Trump was criticised for a series of comments made about female world leaders at the time.
Trump described Theresa May, while she was Prime Minister and after he made a state visit to Britain, as "foolish" and a "disaster".
His relations with then German chancellor Angela Merkel were fraught with difficulties. In 2017, at Nato headquarters in Brussels, he told one Prime Minister that he could not "stand" Merkel because "that woman embodies everything that I hate."
One American diplomat told The Times: "Trump has a history with women that many see as misogynist. It might be best to avoid putting a woman into the role."
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Dutch Prime Minister Mark Rutte is the most likely candidate to be the next Secretary General
Reuters
Tensions have been rising between Trump and Nato after the 77-year-old former President suggested the US might not protect NATO allies who aren't spending enough on defense from a potential Russian invasion.
Trump, speaking during a political rally in South Carolina and appearing to recount a meeting with NATO leaders, quoted the president of "a big country" that he did not name as asking, "Well sir, if we don't pay, and we're attacked by Russia - will you protect us?"
"I said: 'You didn't pay? You're delinquent?' He said: 'Yes, let's say that happened.' No I would not protect you. In fact I would encourage them to do whatever the hell they want. You gotta pay."
More than two dozen women have accused Trump of sexual assault or harassment over the years, and Biden and other European leaders are unwilling to take risks.
The US and British had made attempts to persuade president of the European Commission Ursula von der Leyen to take up the role as Nato lead in order to "Trump-proof" as his election to a second term appears increasingly likely.
Meanwhile Rutte, 57, is expected to be chosen "probably in the first quarter of this calendar year."
His selection is pencilled in for April 4, meaning he will have to leave office as caretaker Dutch leader during protracted coalition talks to find his successor.