The President of Romania, Klaus Iohannis, has recently expressed his ambitions to run for the post of NATO chief.
In the last two years, the Western defense alliance has operated in a challenging security environment, especially after the start of Russia's war in Ukraine.
"I have decided to enter the race for the post of NATO Secretary General", he said.
Dutch Prime Minister Mark Rutte is thought to be leading the race to lead the alliance and replace Soltenberg, after the United States, Great Britain and Germany have expressed support for his candidacy.
However, Hungary has said it will not support Rutten, who has criticized the Hungarian government in the past.
Stoltenberg's successor, who has led NATO for a decade, is expected to be announced shortly before the alliance's summit to be held in July in Washington.