It appears increasingly likely that the 31 NATO members will be unable to coalesce around a candidate to be the alliance's next secretary general and Jens Stoltenberg will be asked to remain in the job for an additional year, multiple sources told CNN.

Although there are a number of prospective candidates, including Danish Prime Minister Mette Frederiksen and British Defense Secretary Ben Wallace, sources said there is a growing chance that there will not be agreement between the members on who should take over during what is a critical period for the defensive alliance as the war in Ukraine continues.

While some inside the White House would have liked to see a female NATO chief elevated for the first time, officials acknowledge that finding consensus has proven difficult.

The United States traditionally does not put forward a candidate, but their backing has major sway, and President Joe Biden views Stoltenberg as "a remarkable leader," in the words of US Secretary of State Antony Blinken.

The former Norwegian prime minister has already extended his tenure once and has served in the role since 2014.

Biden and Stoltenberg met in the Oval Office last week, where the topic of his succession was expected to arise. White House officials have declined to say whether the president asked Stoltenberg to remain in job.

Asked about the prospect, Stoltenberg has repeatedly said he has "no intention of seeking extension of (his) term."

"My only plan is to be focused on my task as secretary general and do my job here until my tenure end this fall and I've really no other plans," he said at a news conference on Monday.

At a news conference in London on Tuesday, Blinken said "we're in very close consultation with our allies and partners to determine where we want to go with NATO and its leadership."

"We're not pushing, promoting any particular candidate," the top US diplomat said.

"The current Secretary General Jens Stoltenberg has been, in President Biden's eyes, a remarkable leader," Blinken said.

"There are also some rather extraordinary people now who people were talking about as the next secretary general. And that's a decision that we will all make collectively as an alliance," he added.