By Steve Holland and Humeyra Pamuk
WASHINGTON (Reuters) - Jens Stoltenberg is expected to be asked to remain as NATO secretary general for another year, according to a source familiar with the discussions and a U.S. official, as the alliance has struggled to decide on a replacement ahead of a mid-July summit in Lithuania.
Stoltenberg's term has already been prolonged three times and he is due to step down in September after nine years as secretary-general of the military alliance.
The Norwegian has broad support among the alliance and continues to be an effective leader, the source, who requested anonymity, told Reuters.
"The (Biden) administration is coming around (to) the idea of Stoltenberg staying on for another year," said the U.S. official, who also spoke on condition of anonymity.
"It doesn't look like there is consensus at the moment within the alliance on his replacement."
The chances of Stoltenberg being asked to extend his tenure for a fourth time have increased as the summit in Vilnius has neared, with allies fearing a show of disunity as NATO continues to respond to Russia's war in Ukraine.
Stoltenberg said in February he was not seeking a further extension to his term. But he has declined to say what he would do if NATO members asked him to stay on.
He stuck to that stance in a press conference on Friday when asked about increasing talk of an extension.
"I have stated again and again that I don't seek (an) extension and there are no other plans than to end my work, and my tenure ends, this fall," he said at NATO headquarters.
Whoever is in the role faces the twin challenges of keeping allies together in supporting Ukraine while guarding against any escalation that would draw NATO directly into a war with Russia.
British Defense Secretary Ben Wallace declared openly that he would like the job. But, as some governments push for a first female NATO secretary-general, Danish Prime Minister Mette Frederiksen also emerged as a serious contender.
But Frederiksen on Thursday backed the idea of Stoltenberg staying on, describing it as a "really good solution".
Frederiksen met U.S. President Joe Biden in Washington earlier this month, before Stoltenberg visited the White House this week for talks with Biden.
U.S. officials believe there is a range of different candidates and that Biden thinks highly of all of them, including Denmark's prime minister, the source said.
Biden believes Stoltenberg has done a tremendous job during a challenging time, a view held by many other allies, the source added.