It is more likely than not that the NATO summit in Lithuania next month will ask Jens Stoltenberg to serve as secretary-general for yet another year due to political differences, vetoes, and personal reluctance.

The United States is skeptical about UK Defense Secretary Ben Wallace's candidacy for the post of NATO secretary-general because a number of US military officials are dissatisfied with him over his measures on Ukraine, The Guardian reported on Sunday.

The US has reservations about Wallace, with some in the military unhappy with the way he has set the pace on the Ukraine issue, the newspaper revealed. 

This comes at a time when, according to The Telegraph, Emmanuel Macron is also trying to block British Defense Secretary Ben Wallace from becoming the next NATO secretary-general due to Brexit. 

The UK Defense Secretary has been mentioned as a possible successor to Jens Stoltenberg when his mandate expires this September. Danish Prime Minister Mette Frederiksen is the front-runner to succeed him.

The Telegraph reported that French officials have informed NATO counterparts that they want an EU frontman. The decision is part of France's ambition to make the bloc more militarily autonomous and less reliant on Washington for security.

That is why if an agreement about an EU candidate, ideally a woman, is not obtained before the summit, Stoltenberg may continue in the position.

Wallace has stated that he prefers the position of Defense Secretary for one of the major European military forces. More than any other nation in Europe, the UK Ministry of Defense maintains close ties with the Ukrainian military, especially at the intelligence level.

But it is suggested that the incoming secretary-general will have to figure out how to strengthen the EU's defense capability -- something the French advocate -- without displacing or compromising NATO's function.

Wallace has never opposed closer EU defense integration, and he even submitted a paper last year outlining how it could be advanced alongside modernizing NATO's own defense strategy. However, he has expressed concerns about increased EU defense cooperation, including arms procurement, if it excludes NATO members that are not EU members, such as the UK.

Danish Prime Minister Mette Frederiksen, who was formerly thought to be the front-runner, insisted last month that she was not running for NATO's top position. That occurred despite speaking with the US President and having a separate meeting with William Burns, head of the CIA. She spent nearly two hours with Joe Biden in what appeared to be a job interview and had just increased Danish defense spending to bring it closer to the 2% of GDP spending recommended by NATO.

A Stoltenberg extension would be a great answer, according to Frederiksen, who was regularly questioned about the matter by the Danish media.

Read: Stoltenberg's NATO tenure likely to be extended

Estonian Prime Minister Kaja Kallas enjoys significant backing among NATO's eastern member states, and despite her recent reelection, she has not ruled herself out.

There is still some doubt regarding her denials of interest in the position among Denmark's Social Democrats, the party Frederiksen represents. Per Stefansen, the Social Democrat district chair in Ringkøbing, Central Jutland, stated that Frederiksen was running for the position, which had previously been held by Anders Fogh Rasmussen, the former Danish Prime Minister.

Before the alliance's 75th anniversary summit in the US the following year, Stoltenberg would maintain continuity if he were to hold onto his job for another year. NATO serves as an advocate but does not actually organize the delivery of weaponry to Ukraine.

When Stoltenberg said earlier in the week, "I am responsible for all decisions that this alliance has to take, except for one. And that is about my future. That is for the 31 allies to decide," he seemed to keep his options open.